Update Rails to Patch Security Vulnerability

Update Rails from 3.2.6 to 3.2.11 for security vulnerability fix
(CVE-2013-0156).
Fix version of active admin to 0.4.4.
Fix Live Preview Bug in Active Admin

Locked pagedown-rails gem to 1.0.0 to fix live preview from rendering
properly.
Remove Manual Security Patch Fix

Updated Rails to 3.2.11 that fixes CVE-2013-0156.