Added Function (F1 - F12), numpad, and other keycodes.

Added keycodesDown() and keycodesHit() functions to assist in seeing which key codes are currently being held down or are pressed.
Renamed keycodes functions to "downKeys" and "hitKeys".
Merge pull request #22 from SolarLune/master

Added Function (F1 - F12), numpad, and other keycodes.