Adds a test suite and intial tests.

I added a few tests for now which should work, even tough 3 fail right now.

I'm not quite sure if the syntax I suggested in https://github.com/adambom/parallel.js/issues/7#issuecomment-15109321 is acceptable or wanted, but I think my tests partially intend to check this syntax, which at the moment is wrong, therefore the failures.