Right rear view added with tap recognizer and other

This pull request adds the possibility to have a rear view shown when moving the front view to the left. This rear view is called lear view (play on word: the Rear view is shown when the front view is moved to the Right, the Lear view when moved to the Left. Lear is the name of a central figure in one of Shakespeare tragedy).
Also added, a tap/slide recognizer on the front view to automatically hide the menu when tapping or sliding the front view when the rear (or lear) view is revealed.
The recognizer does not recognize anything if neither the rear nor the lear view is revealed.

Bug fix: on the iPhone 5, the size of the rear view was not correct. This is now fixed (merge of @bbshih's pull request (#50))