Add chess board to list view
Remove legacy java doc
Remove arguments from LayoutParams constructor - they have no effect
Layout params should be WRAP_CONTENT, WRAP_CONTENT by default
asyncSetup: create solver, parse and add constratins on a background thread
Remove setupComplete boolean - more robust to test if cassowaryModel has been set
Add CassowaryLayoutSetupCallback so clients can wait for setup to complete before attempting to access Cassowary model
Add support for a pre-setup width height ratio.

A layout's pre-setup width to hight ratio can be specified as a decimal e.g 1.77 (16:9)
This is useful for lists and scroll views where a hight or width is needed prior to setup
Added PreSetupTestActivity - tests for pre setup layout state