Laptop Riser with Retention

This is a riser to get my laptop off the desk for increased ventilation. Many other laptop stands hold the computer at an angle, this one sits flat.
The legs are adjustable to fit different shapes of computer.
In the [previous version](http://www.thingiverse.com/thing:950834) the legs would fall out of the hub when moving. This version adds a small retention groove to keep them all together. Because of this, it'll be a bit harder to push the legs into the hub.

Note: you only have to print the .stl files (hub once, and then legsx4). The OpenSCAD files are included.