added more comments.
cosmetic fixes
example showing how to re-use a map background.
added new embedding_map_in_wx.py example, courtesy of Mauro Cavalcanti.
Update sidebar.
added new links to sidebar
Converted API_CHANGES to reST and included it in the documentation tree.
New custom colormap example; and fix typo in Axes.autoscale_view
Improved docstrings in colors.py
Use autoscale_view for contour plot autoscaling
