renamed renderer -> plot in css

Plots were still called renderers in our CSS, now they're called plots. I believe the only place where they're still called renderers is in private and local variables.

For QE, just try some different types of plots, and look for "weird style", like

![screen shot 2014-08-04 at 11 20 20 am](https://cloud.githubusercontent.com/assets/3344958/3801426/0d8d71b6-1c04-11e4-8802-d699a7215135.png)

Close #709.
I've changed this to `scatter-plot`, but I don't think this class is even being used. This is the only place `circle-renderer` appears in our codebase.