added: test for nlp() function to ensure future changes don't break it
added: test for nlp() function to ensure None is returned if there are no matches.
bigfix: it's a hack and will only work for the english language version of 'after' but the 'after' modifier now works and the test passes.
Merge pull request #22 from geoffreyfloyd/master

Fix for testOffsetAfterNoon fails and new tests for the nlp() function