Initial setup of VBInputSourceController

Re:issue #18

- Created skeleton and test data for VBInputSourceController
- Made a fetch for simulated/test data until we have proper users we could fetch from parse for a venue
- Added NSNotification for the user selection

This should be enough to start tying in with other controllers that listen for user input source change events, and then updating when we have a proper user list to fetch from Parse data for all users checked into a particular venue.

It doesn't touch on any other files, so should be safe to pull in.