Added TestTypes.hs as an extra source file to Cabal build

This way, the file will be included in source distributions generated
with `cabal sdist`.
Merge pull request #4 from vlopezj/cabal-test-file

Added TestTypes.hs as an extra source file to Cabal build
Added test for phantom types
Bump version to 0.2.1.0
Merge pull request #5 from vlopezj/test-phantom

Added test for phantom types
Bump version to 0.2.2.0