Use Genni (or Demographer?) for gender validation

http://abel.lis.illinois.edu/cgi-bin/genni/nameprediction.cgi?name=Bo
https://bitbucket.org/mdredze/demographer/src/master/

Recommended at https://twitter.com/aaronclauset/status/1149085117198897153 (which advocates against genderize.io).