Fixed Customizable Mobile Phone Stand

Fixed maths in the original [Mobile Phone Stand](http://www.thingiverse.com/thing:35740) to make it trully customizable.

All angles, lengths and thickness are customizable.

*I discovered this one http://www.thingiverse.com/thing:81117 while making mine, but decided to still do mine and take it as an exercise, plus mine seem to have less glitches*