Break up the model module

The `model` module has historically been one giant module re-exporting
all of the model types, which is somewhere around 100 types. This can be
a lot to look at for a new user and somewhat overwhelming, especially
with a large number of fine-grained imports from the module.

The module is now neatly split up into submodules, mostly like it has
been internally since the early versions of the library. The submodules
are:

- application
- channel
- error
- event
- gateway
- guild
- id
- invite
- misc
- permissions
- prelude
- user
- voice
- webhook

Each submodule contains types that are "owned" by the module. For
example, the `guild` submodule contains, but not limited to, Emoji,
AuditLogsEntry, Role, and Member. `channel` contains, but not limited
to, Attachment, Embed, Message, and Reaction.

Upgrade path:

Instead of glob importing the models via `use serenity::model::*;`,
instead glob import via the prelude:

```rust
use serenity::model::prelude::*;
```

Instead of importing from the root model module:

```rust
use serenity::model::{Guild, Message, OnlineStatus, Role, User};
```

instead import from the submodules like so:

```rust
use serenity::model::channel::Message;
use serenity::model::guild::{Guild, Role};
use serenity::model::user::{OnlineStatus, User};
```

9 files changed, 28 insertions, 26 deletions

diff --git a/src/builder/create_embed.rs b/src/builder/create_embed.rs
index ae0975b..1b15253 100644
--- a/src/builder/create_embed.rs
+++ b/src/builder/create_embed.rs
@@ -17,7 +17,7 @@
 
 use chrono::{DateTime, TimeZone};
 use internal::prelude::*;
-use model::Embed;
+use model::channel::Embed;
 use serde_json::Value;
 use std::collections::HashMap;
 use std::default::Default;
@@ -203,9 +203,9 @@ impl CreateEmbed {
     /// Passing a string timestamp:
     ///
     /// ```rust,no_run
-    /// # use serenity::prelude::*;
-    /// # use serenity::model::*;
-    /// #
+    /// use serenity::prelude::*;
+    /// use serenity::model::channel::Message;
+    ///
     /// struct Handler;
     ///
     /// impl EventHandler for Handler {
@@ -229,9 +229,10 @@ impl CreateEmbed {
     /// Note: this example isn't efficient and is for demonstrative purposes.
     ///
     /// ```rust,no_run
-    /// # use serenity::prelude::*;
-    /// # use serenity::model::*;
-    /// #
+    /// use serenity::prelude::*;
+    /// use serenity::model::guild::Member;
+    /// use serenity::model::id::GuildId;
+    ///
     /// struct Handler;
     ///
     /// impl EventHandler for Handler {
diff --git a/src/builder/create_invite.rs b/src/builder/create_invite.rs
index 269c51c..d91a0e6 100644
--- a/src/builder/create_invite.rs
+++ b/src/builder/create_invite.rs
@@ -14,7 +14,7 @@ use std::default::Default;
 ///
 /// ```rust,no_run
 /// # use serenity::prelude::*;
-/// # use serenity::model::*;
+/// # use serenity::model::prelude::*;
 ///
 /// struct Handler;
 ///
@@ -77,7 +77,7 @@ impl CreateInvite {
     ///
     /// ```rust,no_run
     /// # use serenity::CACHE;
-    /// # use serenity::model::ChannelId;
+    /// # use serenity::model::id::ChannelId;
     /// # use std::error::Error;
     /// #
     /// # fn try_main() -> Result<(), Box<Error>> {
@@ -110,7 +110,7 @@ impl CreateInvite {
     ///
     /// ```rust,no_run
     /// # use serenity::CACHE;
-    /// # use serenity::model::ChannelId;
+    /// # use serenity::model::id::ChannelId;
     /// # use std::error::Error;
     /// #
     /// # fn try_main() -> Result<(), Box<Error>> {
@@ -141,7 +141,7 @@ impl CreateInvite {
     ///
     /// ```rust,no_run
     /// # use serenity::CACHE;
-    /// # use serenity::model::ChannelId;
+    /// # use serenity::model::id::ChannelId;
     /// # use std::error::Error;
     /// #
     /// # fn try_main() -> Result<(), Box<Error>> {
@@ -172,7 +172,7 @@ impl CreateInvite {
     ///
     /// ```rust,no_run
     /// # use serenity::CACHE;
-    /// # use serenity::model::ChannelId;
+    /// # use serenity::model::id::ChannelId;
     /// # use std::error::Error;
     /// #
     /// # fn try_main() -> Result<(), Box<Error>> {
diff --git a/src/builder/create_message.rs b/src/builder/create_message.rs
index bd5996a..a8f22f9 100644
--- a/src/builder/create_message.rs
+++ b/src/builder/create_message.rs
@@ -1,5 +1,5 @@
 use internal::prelude::*;
-use model::ReactionType;
+use model::channel::ReactionType;
 use std::collections::HashMap;
 use std::fmt::Display;
 use super::CreateEmbed;
@@ -23,7 +23,7 @@ use utils;
 /// Sending a message with a content of `"test"` and applying text-to-speech:
 ///
 /// ```rust,no_run
-/// use serenity::model::ChannelId;
+/// use serenity::model::id::ChannelId;
 ///
 /// let channel_id = ChannelId(7);
 ///
diff --git a/src/builder/edit_guild.rs b/src/builder/edit_guild.rs
index 45969fe..b15658c 100644
--- a/src/builder/edit_guild.rs
+++ b/src/builder/edit_guild.rs
@@ -1,5 +1,5 @@
 use internal::prelude::*;
-use model::{ChannelId, Region, UserId, VerificationLevel};
+use model::prelude::*;
 use std::collections::HashMap;
 
 /// A builder to optionally edit certain fields of a [`Guild`]. This is meant
@@ -56,7 +56,7 @@ impl EditGuild {
     /// from the cwd and encode it in base64 to send to Discord.
     ///
     /// ```rust,no_run
-    /// # use serenity::model::GuildId;
+    /// # use serenity::model::id::GuildId;
     /// # use std::error::Error;
     /// #
     /// # fn try_main() -> Result<(), Box<Error>> {
@@ -112,12 +112,12 @@ impl EditGuild {
     /// Setting the region to [`Region::UsWest`]:
     ///
     /// ```rust,no_run
-    /// # use serenity::model::GuildId;
+    /// # use serenity::model::id::GuildId;
     /// # use std::error::Error;
     /// #
     /// # fn try_main() -> Result<(), Box<Error>> {
     /// #     let mut guild = GuildId(0).get()?;
-    /// use serenity::model::Region;
+    /// use serenity::model::guild::Region;
     ///
     /// // assuming a `guild` has already been bound
     ///
@@ -163,7 +163,7 @@ impl EditGuild {
     /// Setting the verification level to [`High`][`VerificationLevel::High`]:
     ///
     /// ```rust,ignore
-    /// use serenity::model::VerificationLevel;
+    /// use serenity::model::guild::VerificationLevel;
     ///
     /// // assuming a `guild` has already been bound
     ///
diff --git a/src/builder/edit_member.rs b/src/builder/edit_member.rs
index e68fc43..ee04829 100644
--- a/src/builder/edit_member.rs
+++ b/src/builder/edit_member.rs
@@ -1,5 +1,5 @@
 use internal::prelude::*;
-use model::{ChannelId, RoleId};
+use model::id::{ChannelId, RoleId};
 use std::collections::HashMap;
 
 /// A builder which edits the properties of a [`Member`], to be used in
diff --git a/src/builder/edit_profile.rs b/src/builder/edit_profile.rs
index 09d3337..d388804 100644
--- a/src/builder/edit_profile.rs
+++ b/src/builder/edit_profile.rs
@@ -21,7 +21,7 @@ impl EditProfile {
     ///
     /// ```rust,no_run
     /// # use serenity::prelude::*;
-    /// # use serenity::model::*;
+    /// # use serenity::model::prelude::*;
     /// #
     /// # struct Handler;
     ///
diff --git a/src/builder/edit_role.rs b/src/builder/edit_role.rs
index 7e2ff17..88c876f 100644
--- a/src/builder/edit_role.rs
+++ b/src/builder/edit_role.rs
@@ -1,6 +1,7 @@
 use internal::prelude::*;
 use std::collections::HashMap;
-use model::{Permissions, Role};
+use model::guild::Role;
+use model::Permissions;
 
 /// A builer to create or edit a [`Role`] for use via a number of model methods.
 ///
@@ -20,7 +21,7 @@ use model::{Permissions, Role};
 /// Create a hoisted, mentionable role named `"a test role"`:
 ///
 /// ```rust,no_run
-/// # use serenity::model::{ChannelId, GuildId};
+/// # use serenity::model::id::{ChannelId, GuildId};
 /// # let (channel_id, guild_id) = (ChannelId(1), GuildId(2));
 /// #
 /// // assuming a `channel_id` and `guild_id` has been bound
diff --git a/src/builder/execute_webhook.rs b/src/builder/execute_webhook.rs
index 6276da1..fb48e96 100644
--- a/src/builder/execute_webhook.rs
+++ b/src/builder/execute_webhook.rs
@@ -17,7 +17,7 @@ use std::default::Default;
 ///
 /// ```rust,no_run
 /// use serenity::http;
-/// use serenity::model::Embed;
+/// use serenity::model::channel::Embed;
 /// use serenity::utils::Colour;
 ///
 /// let id = 245037420704169985;
diff --git a/src/builder/get_messages.rs b/src/builder/get_messages.rs
index e59584f..1032a2f 100644
--- a/src/builder/get_messages.rs
+++ b/src/builder/get_messages.rs
@@ -1,4 +1,4 @@
-use model::MessageId;
+use model::id::MessageId;
 use std::collections::HashMap;
 
 /// Builds a request for a request to the API to retrieve messages.
@@ -29,8 +29,8 @@ use std::collections::HashMap;
 /// # use std::error::Error;
 /// #
 /// # fn try_main() -> Result<(), Box<Error>> {
-/// use serenity::model::{ChannelId, MessageId};
 /// use serenity::builder::GetMessages;
+/// use serenity::model::id::{ChannelId, MessageId};
 ///
 /// let retriever = GetMessages::default()
 ///     .after(MessageId(158339864557912064))