LTe/acts-as-messageable — pull request #20 by aagrawal2001 (2011-12-14 06:04:06+00:00)
Title: Tightening up reply_to and adding a convenience reply method on message

This commit does the following:
- Only allows participants of a message to reply to the message. A message object can easily override the participant? method to allow any special behavior.

- Adds a convenience reply method on the message. In the most common cases, replying to a message means sending a message from the recipient (message.to) to the author (message.from) and this method implements this typical scenario. The reply_to message still remains on the model for backwards compatibility and if anyone wants to get fancy.

- Adds unit tests for the reply_to functionality (the previous tests were part of conversation tests, but the functionality wasn't being tested stand alone)