v1.2.0: - Found and fixed some bugs.

- Added a legend.
- Added a label attribute to each plot for the legend.
- Added some more tests.
- Trying to clean up the mess that is all the internals.
- Added cmaps.
- Promoted some parameters to properties so they can be modified after
inital plot.
- Moved around some scalar stuff to try and make the API more
consistent.