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};
```

6 files changed, 10 insertions, 6 deletions

diff --git a/examples/01_basic_ping_bot/src/main.rs b/examples/01_basic_ping_bot/src/main.rs
index 534da71..3bccb74 100644
--- a/examples/01_basic_ping_bot/src/main.rs
+++ b/examples/01_basic_ping_bot/src/main.rs
@@ -1,7 +1,8 @@
 extern crate serenity;
 
 use serenity::prelude::*;
-use serenity::model::*;
+use serenity::model::channel::Message;
+use serenity::model::gateway::Ready;
 use std::env;
 
 struct Handler;
diff --git a/examples/02_transparent_guild_sharding/src/main.rs b/examples/02_transparent_guild_sharding/src/main.rs
index c1a5bbb..f134fc8 100644
--- a/examples/02_transparent_guild_sharding/src/main.rs
+++ b/examples/02_transparent_guild_sharding/src/main.rs
@@ -1,7 +1,8 @@
 extern crate serenity;
 
 use serenity::prelude::*;
-use serenity::model::*;
+use serenity::model::channel::Message;
+use serenity::model::gateway::Ready;
 use std::env;
 
 // Serenity implements transparent sharding in a way that you do not need to
diff --git a/examples/03_struct_utilities/src/main.rs b/examples/03_struct_utilities/src/main.rs
index 4aafb07..bd2b545 100644
--- a/examples/03_struct_utilities/src/main.rs
+++ b/examples/03_struct_utilities/src/main.rs
@@ -1,7 +1,8 @@
 extern crate serenity;
 
 use serenity::prelude::*;
-use serenity::model::*;
+use serenity::model::channel::Message;
+use serenity::model::gateway::Ready;
 use std::env;
 
 struct Handler;
diff --git a/examples/06_voice/src/main.rs b/examples/06_voice/src/main.rs
index 64738a3..0ac5bb5 100644
--- a/examples/06_voice/src/main.rs
+++ b/examples/06_voice/src/main.rs
@@ -12,7 +12,8 @@ extern crate serenity;
 
 use serenity::client::CACHE;
 use serenity::framework::StandardFramework;
-use serenity::model::*;
+use serenity::model::gateway::Ready;
+use serenity::model::id::ChannelId;
 use serenity::prelude::*;
 use serenity::voice;
 use serenity::Result as SerenityResult;
diff --git a/examples/07_sample_bot_structure/src/main.rs b/examples/07_sample_bot_structure/src/main.rs
index 5ab06e5..67d9589 100644
--- a/examples/07_sample_bot_structure/src/main.rs
+++ b/examples/07_sample_bot_structure/src/main.rs
@@ -19,7 +19,7 @@ mod commands;
 
 use serenity::framework::StandardFramework;
 use serenity::model::event::ResumedEvent;
-use serenity::model::Ready;
+use serenity::model::gateway::Ready;
 use serenity::prelude::*;
 use serenity::http;
 use std::collections::HashSet;
diff --git a/examples/08_env_logging/src/main.rs b/examples/08_env_logging/src/main.rs
index ca6af8f..2f0faaf 100644
--- a/examples/08_env_logging/src/main.rs
+++ b/examples/08_env_logging/src/main.rs
@@ -5,7 +5,7 @@ extern crate serenity;
 
 use serenity::prelude::*;
 use serenity::model::event::ResumedEvent;
-use serenity::model::Ready;
+use serenity::model::gateway::Ready;
 use std::env;
 
 struct Handler;