Remove extra "variable =" which was there for no reason
refactor dendrogram calculation out of plot_dendrogram
move establish_axes to plot()
test plot_dendrogram for both row and col
Added sidecolors tests and fixed erroneous sidecolor making (imagine that, writing tests helps you fix your code!)
Added asserts to check that  the provided side_colors are the correct length
Remove cmap/vmin/vmax from pcolormesh_kws, test establish_axes in a bunch of ways