Change FPS measurement.

Before, FPS was measured with the delta time given to love.update(),
which is only accurate to the millisecond, and was outputted with
print().

Now, FPS are measured with love.timer.getMicroTime(), which is accurate
to the microsecond, and is drawn as text directly to the screen.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	camera.lua
Merge pull request #1 from NecroBumpist/master

Change FPS measurement.