New pattern: rotated triangles

This is just a variation on the existing triangle pattern, but pointing horizontally rather than vertically.

Looks like so:

![screen shot 2014-02-05 at 9 21 42 pm](https://f.cloud.github.com/assets/6104/2094908/1388b3c0-8ed6-11e3-830f-0a9c4f41556d.png)