Run codegen's tests on CI
Run codegen's tests on CI

These tests were broken by https://github.com/sgrif/diesel/pull/103, but
the tests aren't run on Travis currently

cascalheira/diesel,cascalheira/diesel,SoftwareWarlock/diesel,diesel-rs/diesel,diesel-rs/diesel,sgrif/diesel,SoftwareWarlock/diesel,mcasper/diesel,mcasper/diesel,tohou/diesel,tohou/diesel,sgrif/diesel