Improved iPad Air 2 wall mount adapter for Vogel's TMM 125 RingO Flex

This is an updated version based on http://www.thingiverse.com/thing:534007.
An earlier print failed (cracked) after mounting it on the bracket due to the tight-fit caused by the rubber cover that has to fit within the ring.

Changes:
- redesigned the ring completely (clean poly-pattern)
- made the ring diameter exactly fit with a .2mm tolerance
- increase the depth to 5.3mm so the clippers should be able to grasp the inner ring to retain

Printed/tested on an UM2+ printer (100% infill