Revert "Refactor KVO"
Revert "Refactor KVO"

This reverts commit 56477775c001ebb9574ce4e62e62d206f7a45fde.

gaurav1981/DAKeyboardControl,cnbin/DAKeyboardControl,Rusik/DAKeyboardControl,AlexanderMazaletskiy/DAKeyboardControl,danielamitay/DAKeyboardControl,jivesoftware/DAKeyboardControl