I fail to see how this API needs to accommodate transpeople in its 0.1 release.
You have failed at empathy.Speaking to the fluidity of human gender, "Other" is the majority of the spectrum and defaulting to binary is just as naïve as defaulting to ASCII as expected input in an application/API written in 2013.
Restricting yourself that early in the release cycle (and I'm still dubious of the merits of this project), doesn't bode well for its future.
Edit: I just read your comment history and, if I'm not mistaken, you're already biased. Or would you care to elaborate what you wrote here? https://news.ycombinator.com/item?id=6451454