Base with lip, for tool carousel

Remix of the base from [the original](http://www.thingiverse.com/thing:702912), with the empty space filled in and a lip around the edge to keep thin tools from sliding out.

It also thins out the lower thickness, I find it's just as stable without using extra filament.

Credit where it's due, the idea for this came from [gkuzyk](http://www.thingiverse.com/make:126162); no source files were posted so I decided to make a new version of the same idea.

The original base is included here because the SCAD files use it. Ignore the weirdness of of the Thingivese preview of the SCAD files, it will render properly when you download it.