clone function needs to use .properties() rather than __properties__
color test now tests combining lines/scatters on one plot
plotting api now supports combining lines/scatters on one plots
undid hugos dataspec refactor
using sets instead of intersect1d to detect whether colors were specified
added legends
- added legend object to objects.py
- added legend creation into plotting.py
- added legend to Collections locations in base.coffee
- changed default location of legend to upper right
- circle glyph checks for glyph radius prop and uses that in drawing legends