Conference Central app could support men's and women's T-shirt sizes

[karlud]

This is a bit of an issue for real-world tech conferences trying to be welcoming to women.

See: http://geekfeminism.wikia.com/wiki/T-shirts

We could change this to set a better social example for lots of future developers.

Also on course-issues: https://github.com/udacity/course-issues/issues/5263