Some Nose tests for plotly, cleaner renderer, minimal subplot support.

Hi,

I added some support for plotly sub-plotting, but I need to read up a little more on how the Bbox and axes work in matplotlib before it would be more usable. There are a couple Nose tests in the test_plotly.py file that I included.  Also, there are some extra examples in the examples directory that mostly deal with subplotting. Note: none of these changes mess with the exporter. 

Cheers!