Add documentation to drawing and helper functions
Add documentation to drawing and helper functions

Address issue #158

Add documentation to drawing and doctests for helper functions.

The documentation for functions that visualize 2D arrays as not been
created yet. There is significant overlap between the code in these
functions and it should be consolidated in another issue.

awhite40/pymks,XinyiGong/pymks,fredhohman/pymks,davidbrough1/pymks,davidbrough1/pymks