Added GeomDensity class
Docstring updates
Docstring updates
Enabled x axis label for histograms
Finished updating docstrings
Allow users to specify non-callable objects in make_aes
Implemented scale_shape as a class
Added dictionary_union function
Work towards displaying legends properly
Implemented legend display for scatter plots
More progress towards correct legend display
ScaleShape fixes
Fix a mistake with ScaleShape
Make sure the legend is nicely sorted
Added test_rplot.py file
Added docstrings to ScaleConstant class
Finished implementing ScaleShape class, complete with docstrings
Implemented ScaleSize as a class
Implemented ScaleGradient as a class
Implemented ScaleGradient2 as a class