Loosen the versions of the dependencies a little bit

I've set the versions of the dependencies in the gemspec file to be a little more broad, so that projects using rails `master` branch can use `roar-rails`. Otherwise, people will get some versions conflict with `actionpack` and `railties`.

I've also bumped the version to `0.0.11` to distinguish this from the previous release.

[![Build Status](https://travis-ci.org/ncuesta/roar-rails.png?branch=master)](https://travis-ci.org/ncuesta/roar-rails)