Honeycomb mesh

Honeycomb mesh used in [Cool PCB Enclosure](http://www.thingiverse.com/thing:1665075).
It is an optimized version of [Openscad hex grid generator](https://www.thingiverse.com/thing:1296149)

**NEW VERSION** is available at this project:
+ [Parametric Honeycomb Mesh (with chamfered edges)](https://www.thingiverse.com/thing:6782906)