* Added a response-status matcher, for matching against the status code of the response.
   Use like <match response-status="404" class="notfounds" /> (esanchez)

 * Added a ReverseMatcher, which allows you to prefix a match statement with not: to reverse
   the result.  Use like <match path="not:/bad-path" /> (esanchez)

 * Added a boolean collapse-sources attribute on TransformActions
   (append, prepend, replace) which can signal that elements moved
   from the content to the theme should be "fully collapsed" into the
   theme immediately, allowing subsequent actions to act on those
   elements within the theme. (ejucovy)

 * Factored out method ``DeliveranceMiddleware.default_theme(self, environ)``
   so that subclasses can implement custom logic for calculating the global
   default theme per request based on the WSGI environment and the value of
   ``self._default_theme`` which is set by the ``theme_uri`` parameter in
   the paste.deploy configuration.

   The default implementation returns the raw string ``self._default_theme``
   directly.

 * Factored out method ``DeliveranceMiddleware.build_external_subrequest``
   which is called when Deliverance is getting a resource via an external
   subrequest (as opposed to a file:// URL or an internal subrequest to the
   application being wrapped by Deliverance)

   The method returns a webob.Request object; the default implementation
   returns a blank Request with only the header
   ``x-deliverance-theme-subrequest`` set.  Subclasses can override
   this behavior, e.g. to preserve certain headers from the original
   request into subrequests.