Add git pseudo name and email to .travis.yml

See: https://git.wiki.kernel.org/index.php/GitFaq#Git_commit_is_dying_telling_me_.22fatal:_empty_ident_.3Cuser.40myhost.3E_not_allowed.22.2C_what.27s_wrong.3F
See: http://stackoverflow.com/questions/7372970/git-commit-with-no-email