Sum: Major overhaul of packaging and instructions

Major updated README's based on Anaconda Python Distribution
Added a Mac app based on Platypus
Renamed postinstall.py as create_sws_shortcut.py and made it less brittle
Include the screenshot in the source now

Workaround for Mac bug on launch (create and destroy a FileDialog)
Bugfix in the testing code inside mpl_polygon_lasso.py