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)

I guess we could go with the nearest match to the requested point size, since the scale factor has to end up being an integer. This means we'll really only have e.g. something like 6pt, 12pt, 18pt, ... available. I was worried this might confuse users if they set the "point size" to 10pt and got the same result as 12pt.