Changes since 0.4:
* Rack is now managed by the Rack Core Team.
* Rack::Lint is stricter and follows the HTTP RFCs more closely.
* Added ConditionalGet middleware.
* Added ContentLength middleware.
* Added Deflater middleware.
* Added Head middleware.
* Added MethodOverride middleware.
* Rack::Mime now provides popular MIME-types and their extension.
* Mongrel Header now streams.
* Added Thin handler.
* Official support for swiftiplied Mongrel.
* Secure cookies.
* Made HeaderHash case-preserving.
* Many bugfixes and small improvements.
* Fix directory traversal exploits in Rack::File and Rack::Directory.
* SPEC changes.
* New middleware Rack::Lock.
* New middleware Rack::ContentType.
* Rack::Reloader has been rewritten.
* Major update to Rack::Auth::OpenID.
* Support for nested parameter parsing in Rack::Response.
* Support for redirects in Rack::Response.
* HttpOnly cookie support in Rack::Response.
* The Rakefile has been rewritten.
* Many bugfixes and small improvements.