Issue/59 implement adding invites to invite table selectfriends

[saviotsui]

1. Created FacebookClient
2. FirebaseClient
   • createUser
   • updateUser
   • createInviteFor
3. Updates to User Entity
4. SelectFriendsViewController now displays two types of friends to match "taggable_friends", and "friends" from facebook api. Back story is, friends are people that have installed and authorized our app to be used. taggable_friends is theoretically a set of people we can post to their wall to join a game.
   • "friends" returns a persistent id which allows us to id and save a user to the user table
   • "taggable_friends" is a randomized hashcode. we cant save these to our user table. At this time, we do nothing but it is theoretically possible that we can post to their wall to join a game.
5. Join Game from main view
6. Fixing our back buttons so they don't crash out app

[wassupnari]

Thanks for plumbing so many different things! It looks good, I'll merge this in!