Upgrade rails to 3.2.11

* CVE-2013-0156
* https://groups.google.com/forum/#!topic/rubyonrails-security/61bkgvnSGTQ/discussion
* http://news.ycombinator.com/item?id=5028218
Merge pull request #46 from alphagov/rails-3.2.11

Upgrade rails to 3.2.11