purescript.cabal: allow mtl-2.2, transformers-0.4

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
purescript.cabal: add missing tests to tarball

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Merge pull request #546 from trofi/master

Update .cabal file to be a bit friendlier for distributions