Foursqaure SDK + Tests

Closes #16

- Adds foursquare SDK
- Adds URL handler for verbatim:// links
- Adds VBFoursquare (a wrapper for Foursquare2)
- Adds Foursquare to the prefix
- Adds AKLocationManager for location block methods (used in VBFoursquare)
- Merges project files changes (builds locally on 32bit iphone sim)
- Adds XCTestCase+Async for asynchronous test support
- Adds authorization notifications
- Adds authorization methods + test
- Adds venue search method + test
- Converts VBUser back to PFObject
- Adds current user details method + test
Merge pull request #34 from azoff/16-feature-foursquare

Foursqaure SDK + Tests