Merge pull request #636 from joshualy/finite_volume

Contains revisions on the Wave Phenomena Lab, and also the Finite Volume lab by Jared Whitehead
fix plots

Make the plots color and remove very fine gridlines.
modify rc file

Remove colormap setting.  Don't force all plots to be grayscale.
Also make bounding boxes tight by default.
fix image path
Merge pull request #637 from ayr0/pcolor

Matplotlib fixes