Log Message:
Update ruby-rack to 1.5.2.

== Changes

Please note that this release includes a few potentially breaking changes.
Of particular note are:

 * SessionHash is no longer a Hash sublcass
 * Rack::File cache_control parameter is removed in place of headers options

Additonally, SPEC has been updated in several areas and is now at 1,2.

A new SPEC section was introduced that provides two server-optional IO hijacking
APIs. Further information on these APIs will be made available by the community
in good time. In the mean time, some information can be found in the original
pull request: https://github.com/rack/rack/pull/481

* January 21st, 2013: Thirty third public release 1.5.0
  * Introduced hijack SPEC, for before-response and after-response hijacking
  * SessionHash is no longer a Hash subclass
  * Rack::File cache_control parameter is removed, in place of headers options
  * Rack::Auth::AbstractRequest#scheme now yields strings, not symbols
  * Rack::Utils cookie functions now format expires in RFC 2822 format
  * Rack::File now has a default mime type
  * rackup -b 'run Rack::File.new(".")', option provides command line \ 
configs
  * Rack::Deflater will no longer double encode bodies
  * Rack::Mime#match? provides convenience for Accept header matching
  * Rack::Utils#q_values provides splitting for Accept headers
  * Rack::Utils#best_q_match provides a helper for Accept headers
  * Rack::Handler.pick provides convenience for finding available servers
  * Puma added to the list of default servers (preferred over Webrick)
  * Various middleware now correctly close body when replacing it
  * Rack::Request#params is no longer persistent with only GET params
  * Rack::Request#update_param and #delete_param provide persistent operations
  * Rack::Request#trusted_proxy? now returns true for local unix sockets
  * Rack::Response no longer forces Content-Types
  * Rack::Sendfile provides local mapping configuration options
  * Rack::Utils#rfc2109 provides old netscape style time output
  * Updated HTTP status codes
  * Ruby 1.8.6 likely no longer passes tests, and is no longer fully supported

* January 28th, 2013: Thirty fourth public release 1.5.1
  * Rack::Lint check_hijack now conforms to other parts of SPEC
  * Added hash-like methods to Abstract::ID::SessionHash for compatibility
  * Various documentation corrections

* February 7th, Thirty fifth public release 1.5.2
  * Fix CVE-2013-0263, timing attack against Rack::Session::Cookie
  * Fix CVE-2013-0262, symlink path traversal in Rack::File
  * Add various methods to Session for enhanced Rails compatibility
  * Request#trusted_proxy? now only matches whole stirngs
  * Add JSON cookie coder, to be default in Rack 1.6+ due to security concerns
  * URLMap host matching in environments that don't set the Host header fixed
  * Fix a race condition that could result in overwritten pidfiles
  * Various documentation additions