Update activerecord (and activesupport)

The Gemfile.lock specified 3.2.2 which is unfortunately vulnerable to
the following security issues:

CVE-2013-0155
CVE-2012-5664
CVE-2012-2695
CVE-2012-2661
Merge pull request #48 from prognostikos/upgrade-active-record

Update activerecord (and activesupport)