(feat) Added Response.send(Status, Data)

This is a really common use case and right now it requires:

```rust
res.status = NewStatus;
try!(res.write(my_body.as_bytes()));
```

After:

```
res.send(NewStatus, my_body);
```

Much better and extremely, extremely common.

send will
Forward write errors ...

You don't need to repeat the function names (trait names, etc.). `rustdoc` does it for us.