Added joystick vibration support for most common controllers (resolves issue #159).

Added Joystick:setVibration(left, right), Joystick:getVibration, and Joystick:isVibrationSupported.
left and right are numbers between 0 and 1 which correspond to the strength of the gamepad's left and right rumble motors, if it has them.

src/scripts/boot.lua

@@ -1502,11 +1502,17 @@ function love.errhand(msg)
 		end
 	end
 
-	-- Load.
+	-- Reset state.
 	if love.mouse then
 		love.mouse.setVisible(true)
 		love.mouse.setGrabbed(false)
 	end
+	if love.joystick then
+		-- Stop all joystick vibrations.
+		for i,v in ipairs(love.joystick.getJoysticks()) do
+			v:setVibration()
+		end
+	end
 	if love.audio then love.audio.stop() end
 	love.graphics.reset()
 	love.graphics.setBackgroundColor(89, 157, 220)