Add support for UIPickerViews in Subliminal
Support Picker controls that aren't used as the inputView for a text field

Other behavior added:
 - Special case UIDatePicker to not search below that element as it can significantly deteriorate performance
 - Added a series of test cases for both UIDatePicker and UIPickerView
 - Ensure that all the functionality works on both iOS6 and iOS7
PR feedback
PR feedback: Fixing documentation and some test names
Merge pull request #211 from justinseanmartin/jmartin/support-pickerview-controls

Add support for UIPickerViews in Subliminal
Button can't be found within a table view header
Add a test case showing the issue