Update doctests for Context changes

Due to the Context having many methods removed, the doctests were
failing.

Update the doctests to use alternative methods to accomplish the same.

Example:

Before:
```rust
context.say("hi");
```

After:
```rust
message.channel_id.say("hi")
```

1 files changed, 2 insertions, 2 deletions

diff --git a/src/ext/framework/create_command.rs b/src/ext/framework/create_command.rs
index 357a597..68319af 100644
--- a/src/ext/framework/create_command.rs
+++ b/src/ext/framework/create_command.rs
@@ -54,8 +54,8 @@ impl CreateCommand {
     ///         .desc("Replies to a ping with a pong")
     ///         .exec(ping)));
     ///
-    /// fn ping(context: &mut Context, _message: &Message, _args: Vec<String>) -> Result<(), String> {
-    ///     let _ = context.say("Pong!");
+    /// fn ping(_context: &mut Context, message: &Message, _args: Vec<String>) -> Result<(), String> {
+    ///     let _ = message.channel_id.say("Pong!");
     ///
     ///     Ok(())
     /// }