Update Rails to 3.1.12 and json to 1.7.7 for Security Reasons.

* Rails: 3.1.11
* CVE-2013-0269: Denial of Service and Unsafe Object Creation Vulnerability in JSON
* CVE-2013-0276: Circumvention of attr_protected
* CVE-2013-0277: Serialized Attributes YAML Vulnerability with Rails 2.3 and 3.0
* Rails: 3.1.12
* CVE-2013-1855: XSS vulnerability in sanitize_css in Action Pack
* CVE-2013-1856: XML Parsing Vulnerability affecting JRuby users
* CVE-2013-1857: XSS Vulnerability in the `sanitize` helper of Ruby on Rails
* CVE-2013-1854: Symbol DoS vulnerability in Active Record