Car-Phone-Cup-Holder v2

This 'thing' supersedes [version 1](http://www.thingiverse.com/thing:271895).

V2 is superior to v1 because:

* it is simpler (less plastic), and comes as a single piece (no welding required).
* the base in v1 is too thin (2mm) - it buckled in the heat / sun inside my car. The base in v2 is 6mm-thick.
* the flanges on the base of v1 (designed to slot into the cup-holder) sometimes failed to work properly when cornering (phone + holder ended up on the floor of the car).
* the 'hooks' ar