Fix a typo in challenges
Disable XML parameters parsing in requests

Related to CVE-2013-0156. Find more info here:
https://groups.google.com/forum/?fromgroups=#!topic/rubyonrails-security/61bkgvnSGTQ

Not upgrading to Rails 3.2.11 yet, since it
may have introduced some new issues during those
hastily pushed security updates.
[Security] Upgrade Devise to 2.2.3

More info here:
http://blog.plataformatec.com.br/2013/01/security-announcement-devise-v2-2-3-v2-1-3-v2-0-5-and-v1-5-3-released/
[SECURITY] Update Rack to latest stable on 1.4.x branch

Addresses a timing attack, which could
allow for remote code execution. References:
https://bugzilla.redhat.com/show_bug.cgi?id=909071
https://github.com/rack/rack/commit/0cd7e9aa397f8ebb3b8481d67dbac8b4863a7f07