Use travis (bug 1066167)

Fixes [bug 1066167](https://bugzilla.mozilla.org/show_bug.cgi?id=1066167)
It does run test-amo-validator also: cf https://github.com/mozilla/amo-validator/pull/264/files#diff-354f30a63fb0907d4ad57269548329e3R7 and https://github.com/mozilla/amo-validator/pull/264/files#diff-b91f3d5bd63fcd17221b267e851608e8R13