Fourth development snapshot for Zend Framework 2.0.

This snapshot includes:

 - The "Dispatchable" and related interfaces (Zend\Stdlib\Dispatchable,
   MessageDescription, RequestDescription, and ResponseDescription)

 - A fully refactored HTTP component
   - Rewritten URI component, with better and more extensible support
     for an array of different URI schemas, as well as more flexible
     path and parameter decomposition and serialization.

   - Adds HTTP versions of the Stdlib Request and Response interfaces,
     along with full-fledged support for standard HTTP headers.

   - A rewritten HTTP client that consumes Http\Request objects and
     produces Http\Response objects.

   - Two additional HTTP client implementations that provide a
     convenience API around the base HTTP client. One is static, and
     allows for simple one-off requests:

         $response = ClientStatic::get($uri);
         $response = ClientStatic::post(
            $uri,
            array('foo' => 'bar'),
            array('Content-Type' => ClientStatic::ENC_URENCODED)
         );

     The other largely mimics the Zend Framework 1.X HTTP client, and
     proxies functionality to the Request object when appropriate.

 - Updated all docbook sources to DocBook 5 formatting standards.

 - Merging of more than 50 pull requests made by community members,
   ranging from one-liner documentation changes to sweeping fixes to the
   testing repository (including fixing most assertions deprecated in
   PHPUnit 3.5.0).

We will be refactoring all components using the HTTP client in an
upcoming milestone to ensure they continue to work, and will also
post a blog entry and documentation page containing tips.

This snapshot should NOT be used in production, as it is considered
pre-pre alpha quality.