Limit tested Python versions
Limit tested Python versions

Ubuntu 18.10 (where I'm building images now) is 3.5.  Removing anything
before that.

rolandgeider/wger,wger-project/wger,wger-project/wger,rolandgeider/wger,petervanderdoes/wger,wger-project/wger,petervanderdoes/wger,rolandgeider/wger,wger-project/wger,petervanderdoes/wger,rolandgeider/wger,petervanderdoes/wger