Add more gender-non-conforming terms

[patcon]

Hiya! Sorry was a little slow on the uptake with #31, but here's a first-pass suggestion

See: http://nikkistevens.com/open-demographics/questions/gender.html

[patcon]

Happy to switch to regex form in the rest of the list, if you think this is an ok approach :)

[ajdavis]

This is very cool, thank you! Are you willing to add a couple tests to test_declared_gender.py? The new code need not be tested exhaustively but I'd a like a couple tests to prove the regexes work as we expect.