Gamepad haptic feedback support [proposal]

[cyberarm]

Add methods to Gosu
Gosu.gamepad_[haptic|rumble]?(id) - [boolean] whether gamepad supports haptic feedback
Gosu.gamepad_[pulse|rumble](id, duration, strength) - [void] vibrate given gamepad
Gosu.gamepad_[pulse|rumble]_stop(id) - [void] halt all force feedback for gamepad

if Gosu.gamepad_haptic?(0) # gamepad_id
  Gosu.gamepad_pulse(0, 150, 0.75) # gamepad_id, duration in ms, strength as value between 0.0 and 1.0
end

SDL Wiki on Force Feedback