Changed the appNetUser property of XIGUserMatcher to not be a signal anymore.

The appNetUser property is now instead computed before the
XIGUserMatcher creation. This makes the processing of the XIGUserMatcher
much easier in the tableview cells.
Add FilterViewController displayed at the bottom of the Friends screen.

The Friends screen re-uses the Semi-modal view controller to display
both the TwitterUsersTableVC and the FilterVC.
Resize Friends screen tableview to not be behind the filter bar.

It is much easier to resize the tableview in code, I hence deleted
the XIB and build view hierarchy in code as it is very simple.
updated ReactiveCocoa
Dependecy Injection of the RACSignal into the Friends tableVC.

This allows the Friend VC to be reusable with usermatchers signal
filtered in different ways.
Add ability to change filter on Friends screen.

Add a container VC which display 1 selected VC out of an array of VCs.
It is used to hold 3 UserMatchersTableVC, 1 for
each possible value of XIGUserFilter, and switch the displayed VC based
on the selected filter in the XIGUserFilterVC.
Add UIColor category and a notification banner library
Monitor reachability status and display an error banner when no internet.
Merge branch 'FilteringFriends'