Travis build failures on 3.04.x branches

[Tom Morris]

Because there's no .travis.yml file on the 3.04.x branches, Travis attempts to do a default Ruby build, which obviously doesn't get very far before failing.

Although the .travis.yml file on master says to build only the master branch, this has no effect because it's not visible on the other branches.

We should be able to disable builds on those branches by logging in to Travis or, perhaps better, we could copy the .travis.yml file over so that we've got CI coverage for the release branches in case we do more releases.

Tom