Added more combinators (pair-of, elements)
Read the comments for more info
Changed module to qc since it's shorter
Removed comment about shrinking (not supported yet) and added some primitive generators
Moved to qc fold instead of quickcheck folder
since I renamed the guile module and that's necessary for some reason
I also finished up with the combinators / basic generators I'm
providing for the library, or at least with the ones I had initially
had in mind.
Renamed to something a bit more descriptive than 'list-gen'