Update Rack - CVE-2013-0263 and CVE-2013-0262

Updated Rack from 1.4.3 to 1.4.5

Ref: http://rack.github.com/

https://support.cloud.engineyard.com/entries/23128773-February-8-2013-Rack-Vulnerabilities-CVE-2013-0263-CVE-2013-0262