Fix #28: better deadzone and overlap for diagonals

[robsdedude]

First of all I've changed the code to correct for the weird rotational offset on the d-touch-pad. Your code was aware of that issue but only for the case where len(self._pad_evts[pos]) == 4. I also tweaked the default d-pad deadzone in the x-box script. It feels snappy and god to use, please give it a try. I also decided to allow multiple buttons to be pressed (i.e. diagonals) for the case where len(self._pad_evts[pos]) == 4.

EDIT: Also worth to mention, I changed the angle concept to just use the plain distance to the axes. This might be debatable, but especially for the d-pad that makes perfect sense. It means "as soon as you leave the grooves indicating straight directions, you input a diagonal".

I hope you find the time to test this out and merge it.