Replaced class and instance level `send`

Replaced with `__send__` from std lib

* `send` can now be overridden to be more semantically meaningful
  * `message.send(user_id)` as opposed to `message.send_message(user_id)`
* `__send__` makes it clear that the reflective version is intended
Merge pull request #1479 from seanpdoyle/master

Replaced class and instance level `send`