add card brand logo images and small icons
create WPYTextField
[bugfix] remove space in MasterCard
declare textfield in card field as public
WPYMenuDisabledTextField subclass from WPYTextField
adjust position of rightview in textfield
show brand logo while typing
define & declare updateValidityView in abstractfield
hide brand logo in number field if validation failed 
at textdidendediting.
show checkmark when value is valid.
refactor out creation of right view into abstract
class
group methods in abstractcardfield
show checkmark when pay button is set to complete