factor out setting text from initializer to setter
method in WPYAbstractCardField
create WPYNumberFieldModel
create WPYNumberFieldModelTest file
fix test case expecting @"Master Card" to @"MasterCard"
define brand name as constant string
use constant string over string literals
refactor out logic in numberfield into model
update amex brand image
fix bug that month missing padding
refactor out logic code in abstract field to model
adjust to changes in superclass and update tests
factor out logic code in expiryfield to a model
factor out logic code in name field into its own model
factor out logic code in cvcfield into a model
remove all logic related code from number field
create a template method instead of allowing override
declare setCardValue method in AbstractFieldModel
call updateBrand in textFieldDidChange
define setCardValue in WPYNumberFieldModel
define setCardValue in ExpiryFieldModel