Upgrade Rails to 3.2.13

Includes fixes for:

* [CVE-2013-1854]
* [CVE-2013-1855]
* [CVE-2013-1856]
* [CVE-2013-1857]
Upgrade to Rails 3.2.13

For now uses dev version of shoulda-matchers.
Remove deprecated delegate matcher.

These tests are here to ensure that delegate calls won't be removed
accidentally.
Fix deprecation warnings after upgrade to rspec 2.13
Upgrade refs to shoulda-matchers.

Apparently the commits were squashed.
Merge pull request #76 from alphagov/upgrade_rails_to_3.2.13

Upgrade rails to 3.2.13