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.
We should settle on a convention for whether or not we want to use a space before parentheses. From there, we can make it the standard from now on since we have both cases (no space and one space) in our code right now. @psybuzz what do you think? I think I'd prefer going with one space before the parentheses as our convention.