Updated library of geometric algorithms

Today I released an updated version of the library of geometric algorithms.

1. It now uses stack as a building tool.
2. All literate Haskell (*.lhs) files were migrated to pure *.hs files (with a Groovy script I wrote today)
3. I added HSpec as a unit testing library and wrote a few tests (back in the 90s when the project started, there were no unit tests).