This will prevent someone to think that Paperclip test suite for master branch is currently failing, as the build was failed on a WIP branch, not the main branch.

http://travis-ci.org/#!/thoughtbot/paperclip/builds.

I think it's OK to have the bugfix for MongoDB in the plugin.

This reverts commit cde22564.

Add rubinius to travis testing

Bump rails 3_1 version to rc6

This reverts commit fe01ae69.

It seems like that JRuby on travis-ci is broken[1], so we shouldn't test against it to reduce the false-positive result. I've run the test locally, and it passed just fine[2].

[1]: http://travis-ci.org/#!/thoughtbot/paperclip/builds/79181
[2]: https://gist.github.com/299686b412f9ad878e16

Update Gemfile to make sure we can run the test locally, and also upgrade Rails 3.1 beta to latest version

Closes #534, closes #538

We already merged it in 6a10b358 and 0708cd43

This reverts commit ff3929ee.