Added instance initializers, public formatter property, and a method to register the currency uuntilas an observer of the passed in UITextfield. Also added a decimalValue method on an NSString category.
Added a toggleFractionsDigits method to switch between dealing with regular two decimal digit currency and three or four decimal digits.
Removed switch in favor of using two or four minimum fraction digits.
Fixed bug causing integer digits to not set correctly.
Added an active property that can be used as a return value for a UITextFieldDelegate deciding whether to change characters. Also removed unnecessary nsstring category and method decimalValue.
Added condition to handle differences in scale when setting the active property. Also set textField.text to nil when toggling fraction digits.
Added method to retrieve a removableCharacterSet. Also added an NSString category with stringByRemovingCharactersInSet, and stringByReplacingCharactersInSet:withString: methods.