Renamed manageKeys() to manageKeyboard().
Added isKeyDown() and manageKeyboard().
Routines::isKeyDown() is a public proxy for key_down_; it returns true if a key on the keyboard is currently being pressed down, and false if the key has been released or has not been pressed before. Routines::manageKeyboard() will dictate whether or not key_down_ is true or false. It may be a good idea to merge these into one method.