While RubyGems is generally available, travis-build does not depend on it as of now (at least to my knowledge), so this would add a dependency.

We “[highly discourage](http://about.travis-ci.org/docs/user/languages/javascript-with-nodejs/#Choosing-Node-versions-to-test-against)” using anything but 0.6 for 0.6 versions, so the only bug I see with this code is that it would also match version 0.60. A better solution might be a regex (`/\A0\.6(\.*)?\z/ =~ config[:node_js]`) or using `split` (`config[:node_js].split('.')[0..1] == %w(0 6)`).

As far as I know, "0.6" just means "a version where the major version is 0 and the minor is 6 and the rest can be anything", so I don't see how this is less reliable.