Make builders mutably borrowed

Change the builders so that they are now mutably borrowed, accepting
`&mut self` instead of `self`. Their methods now return `()` instead of
`Self`.

Upgrade path:

Change code such as the following:

```rust
channel.send_message(|m| m
    .embed(|e| e
        .description("test")
        .title("title")));
```

to the following style:

```rust
channel.send_message(|mut m| {
    m.embed(|mut e| {
        e.description("test");
        e.title("title");

        e
    });

    m
});
```

Closes #159.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/framework/standard/help_commands.rs b/src/framework/standard/help_commands.rs
index 84a1399..c7b9f68 100644
--- a/src/framework/standard/help_commands.rs
+++ b/src/framework/standard/help_commands.rs
@@ -240,7 +240,7 @@ pub fn with_embeds<H: BuildHasher>(
                 &help_options.striked_commands_tip_in_dm
             };
 
-            if let Some(ref striked_command_text) = striked_command_tip{
+            if let Some(ref striked_command_text) = striked_command_tip {
                 embed.colour(help_options.embed_success_colour);
                 embed.description(format!(
                     "{}\n{}",