Build: remove Go 1.4 support
Build: remove Go 1.4 support

Reviewers: shahms, zarko

Reviewed By: zarko

Differential Revision: https://phabricator-dot-kythe-repo.appspot.com/D755

bzz/kythe,bzz/kythe,bzz/kythe,kythe/kythe,bzz/kythe,kythe/kythe,legrosbuffle/kythe,legrosbuffle/kythe,benjyw/kythe,benjyw/kythe,bzz/kythe,bowlofstew/kythe,legrosbuffle/kythe,bowlofstew/kythe,kythe/kythe,kythe/kythe,legrosbuffle/kythe,bowlofstew/kythe,legrosbuffle/kythe,bzz/kythe,bzz/kythe,bowlofstew/kythe,bzz/kythe,kythe/kythe,legrosbuffle/kythe,benjyw/kythe,bowlofstew/kythe,bzz/kythe,benjyw/kythe,bowlofstew/kythe,kythe/kythe,kythe/kythe,benjyw/kythe,bzz/kythe,benjyw/kythe,bowlofstew/kythe,kythe/kythe,benjyw/kythe,legrosbuffle/kythe,benjyw/kythe,bowlofstew/kythe,legrosbuffle/kythe,legrosbuffle/kythe,bowlofstew/kythe,kythe/kythe,bzz/kythe,bowlofstew/kythe,benjyw/kythe,benjyw/kythe,bzz/kythe,legrosbuffle/kythe,benjyw/kythe,benjyw/kythe,kythe/kythe,kythe/kythe,legrosbuffle/kythe,bowlofstew/kythe