Fixed up de-duplication issues

This finishes up the de-duplication of adding users to a conversation as well as adding a conversation to a user's conversation list.  It should also restore functionality to many things that are currently broken on master.

Conversation.js is getting a bit messy and bloated, perhaps a refactoring should be considered in a future PR.
Would it be best to tab back the last two lines of this comment so that it matches up with the rest of the comment? I think that'd make it more clear to read.