BUG: Fix undefined variable
DOC: Added example to plot_fit. Included plot functions in docs.
DOC: Clean up plotting examples and use pandas
Merge branch 'fix-630'. Closes #751. Closes #630.

* fix-630:
  DOC: Clean up plotting examples and use pandas
  DOC: Added example to plot_fit. Included plot functions in docs.
  BUG: Fix undefined variable