Restructure modules

Modules are now separated into a fashion where the library can be used
for most use cases, without needing to compile the rest.

The core of serenity, with no features enabled, contains only the
struct (model) definitions, constants, and prelude. Models do not have
most functions compiled in, as that is separated into the `model`
feature.

The `client` module has been split into 3 modules: `client`, `gateway`,
and `http`.

`http` contains functions to interact with the REST API. `gateway`
contains the Shard to interact with the gateway, requiring `http` for
retrieving the gateway URL. `client` requires both of the other features
and acts as an abstracted interface over both the gateway and REST APIs,
handling the event loop.

The `builder` module has been separated from `utils`, and can now be
optionally compiled in. It and the `http` feature are required by the
`model` feature due to a large number of methods requiring access to
them.

`utils` now contains a number of utilities, such as the Colour struct, the
`MessageBuilder`, and mention parsing functions.

Each of the original `ext` modules are still featured, with `cache` not
requiring any feature to be enabled, `framework` requiring the `client`,
`model`, and `utils`, and `voice` requiring `gateway`.

In total the features and their requirements are:

- `builder`: none
- `cache`: none
- `client`: `gateway`, `http`
- `framework`: `client`, `model`, `utils`
- `gateway`: `http`
- `http`: none
- `model`: `builder`, `http`
- `utils`: none
- `voice`: `gateway`

The default features are `builder`, `cache`, `client`, `framework`,
`gateway`, `model`, `http`, and `utils`.

To help with forwards compatibility, modules have been re-exported from
their original locations.

1 files changed, 12 insertions, 2 deletions

diff --git a/src/model/channel/embed.rs b/src/model/channel/embed.rs
index b278622..9e35ea5 100644
--- a/src/model/channel/embed.rs
+++ b/src/model/channel/embed.rs
@@ -1,7 +1,11 @@
-use ::utils::builder::CreateEmbed;
-use ::utils::Colour;
 use ::internal::prelude::*;
 
+#[cfg(feature="utils")]
+use ::utils::Colour;
+
+#[cfg(feature="model")]
+use ::builder::CreateEmbed;
+
 /// Represents a rich embed which allows using richer markdown, multiple fields
 /// and more. This was heavily inspired by [slack's attachments].
 ///
@@ -17,8 +21,13 @@ pub struct Embed {
     /// Information about the author of the embed.
     pub author: Option<EmbedAuthor>,
     /// The colour code of the embed.
+    #[cfg(feature="utils")]
     #[serde(default, rename="color")]
     pub colour: Colour,
+    /// The colour code of the embed.
+    #[cfg(not(feature="utils"))]
+    #[serde(default, rename="color")]
+    pub colour: u32,
     /// The description of the embed.
     ///
     /// The maximum value for this field is 2048 unicode codepoints.
@@ -53,6 +62,7 @@ pub struct Embed {
     pub video: Option<EmbedVideo>,
 }
 
+#[cfg(feature="model")]
 impl Embed {
     /// Creates a fake Embed, giving back a `serde_json` map.
     ///