Copied this lasso example from the internet:
http://matplotlib.org/examples/event_handling/lasso_demo.html
Added backend-dependent bugfix: manually disabling 'supports_blit'
Refactored the demo to be more flexible with input filetype.

I also added "small_demo" to run a dendrogram on a much smaller dataset. I'd prefer to restrict it to something like Orion but whatevs, at the moment.
Added source of lasso_experimental.