ENH: Add console visual

Ready for review/merge.

Closes #418.

Example output:

![screenshot from 2014-09-02 10 27 45](https://cloud.githubusercontent.com/assets/2365790/4122587/1b455534-32c6-11e4-9821-e0ca0e949bd6.png)

Ah, I see now this uses point sprites. I thought you were setting up a mesh of triangles.
I assume 2 triangles would rasterize more quickly, but that's not so important given it would require a lot of other restructuring..