Add plotting/pandas functionality for single-var and multi-var sweeps

[edmundsj]

Currently, plotting only works vs. wavelength, it would be nice to expand this to any single-variable or multi-variable sweep. Integrating heat map plotting for 2d sweeps. This would be enabled by the results being convertible into a pandas array or something of the like.

turning the results dictionary into a Results object and then adding a plot() method to that seems like the most elegant way to do this.

[edmundsj]

Single-variable sweeps can now be plotted easily with the Results.plot() method. as of a9f9e59, and the results are available as simple arrays.