Rewrite the library to use Futures

Rewrites the library to use Futures. This rewrites all of the gateway,
client, cache, most model methods, HTTP, and in a later commit the
framework and voice.

HTTP has been mostly rewritten to be ergonomic so that it can be used by
the user, and has been upgraded to hyper v0.11.

The gateway now uses `tokio-tungstenite` v0.4.

The client isn't yet in a working state.

The models now have a `client` optionally attached to them to make use
of `http` and `cache`-utilizing methods. The client isn't needed, in the
case that someone is using the library just to deserialize models.

The cache is now built around `Rc`s and `RefCell`s, instead of `Arc`s
and `RwLock`s.

Refer to example 01 for a working example. Much of the library still
doesn't work.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/model/error.rs b/src/model/error.rs
index ea919bc..58fe647 100644
--- a/src/model/error.rs
+++ b/src/model/error.rs
@@ -73,6 +73,9 @@ pub enum Error {
     /// When attempting to delete below or above the minimum and maximum allowed
     /// number of messages.
     BulkDeleteAmount,
+    /// The client wasn't present on the model when it was expected to be, e.g.
+    /// when performing a cache or HTTP operation on it.
+    ClientNotPresent,
     /// When attempting to delete a number of days' worth of messages that is
     /// not allowed.
     DeleteMessageDaysAmount(u8),
@@ -131,6 +134,7 @@ impl StdError for Error {
     fn description(&self) -> &str {
         match *self {
             Error::BulkDeleteAmount => "Too few/many messages to bulk delete",
+            Error::ClientNotPresent => "The client wasn't present on the model",
             Error::DeleteMessageDaysAmount(_) => "Invalid delete message days",
             Error::EmbedTooLarge(_) => "Embed too large",
             Error::GuildNotFound => "Guild not found in the cache",