Ref #2 - Deleting friends from user index works

Removed legacy 'inverse_friendship' code from friendships_controller
destroy action
Added class method to Friendship model for finding a particular
friendship based on two user ids
The new class method is now used in the users_index view to remove
friends
Ref #2 - user/index shows friend status correctly

-Added some class methods to Friendship model, in order to grab
friendships of different types (accepted, pending, owner of friendship)
-Expanded the 'is_friends_with?' method to not only find a friendship
with the given user_id, but also determine if its been accepted or
pending using the new Friendship class methods.
-Updated the conditionals on the user/index page to display different
links depending on the status of the friendship
Ref #2 - Fixed users/show friendships display

-Adjusted pending instance method in the user model to account for
friendships where the user isn't the recipient of a request
-Added a conditional to users/show so the friendships now display
properly for each user.
Merge pull request #6 from mgabrel/2-delete-friendships

2 delete friendships
Added tracking to friendships

-Updating tracking settings for disc/game/friendships
-Still need to account for deleted items in a public activity breaking
the front page