MBContactPicker should implement UITextInput protocol

[vincentjames501]

On the iPhone 6/6+ when you have the landscape keyboard, clicking on a preexisting item then clicking the 'forward' and 'backwards' arrow will cause the application to crash with something like the following:

Application Specific Information:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException',
 reason: '-[MBContactCollectionView selectedTextRange]: 
unrecognized selector sent to instance 0x13c902c00'

By implementing the UITextInput protocol I can prevent it from crashing however you can't continue to go forward and back once you've selected an item in the picker.