Rename buttonColor -> originalBackgroundColor
Simplify abridged init method
No need to validate radius as it is always a valid CGFloat value
Do not override Interface Builder font
Override setBackGroundColor instead of using makeFlat:withBackgroundColor:

Enables changing the background color after initialization
Move action setting out of setter
Add missing control events to actions
Merge pull request #8 from rivera-ernesto/refactor

Refactor