Add vector class and use instead of np.array
Blur only when Scipy and Numpy can be imported
Don't make scipy and numpy hard dependencies

... and remove PIL that is not used anyway.
increased acceptable rms for input tests
added expected test image for thick lines feature
Merge branch 'np-free' of https://github.com/matze/shaape into develop
fixed anchor position
fixed chordfree calculation with better ccw algorithm
fixed x-y order in ccw algorithm