Modify create_request() to set request._messages.

* It assigns an iterable DummyStorage object to the
  attribute.
* You can override it with a keyword argument of 'messages'.
Rewrite IntegrationTestCase.

* Can now deal with function-based views (subclass it with
  view=[view_method] rather than view_class=[class]), and
  provides a get_view() method to abstract over accessing
  them.
* access_view now accepts an optional request kwarg, and
  will create its own request if one isn't supplied.
* It also attaches the request (created or otherwise) to
  the returned response object, so that it can be used
  elsewhere without having to pass tuples around or anything
  silly like that.
* render_to_str now checks for this attached request, and
  uses that in the render() call if possible.
* access_and_assert_view has been renamed to
  access_view_and_render_response, which is a bit of a
  mouthful, but much clearer.
* Lots of commenting.  Possibly more to come.
More comments! Comments are good.
Clean up now-unnecessary DummyStorage().
Comment terminology fix.
Use a list for DummyStorage() for ordering.
Move parameters around for python 2 compatibility.
Fix a method call to roll in reordering.
Change get_view() to simplify the API.

* You now set self.view for both class-based and function-
  based views.
Clean up get_view and improve commenting.
Roll optional parameters into kwargs.
Rename get_view() to get_view_method() for clarity.
Remove largely-unnecessary 'messages' kwarg.
Rename get_view() again.
Fixes for broken function-based view handling.

* The request parameter was being passed into access_view
  in the wrong way.
* Just setting `view = [view_func]` on a test class doesn't
  work, since it binds the function to the class as a
  method.  Wrapping it in `staticmethod()` avoids this, so
  add that to the docstring.
Add a way to attach a session to a request.

* Use it by default in IntegrationTestCase, because integration
  tests are the sort of tests that want sessions (logged-in
  users, for instance).
Move get_view() to BaseRequestTestCase.
Merge pull request #20 from incuna/refactor-for-sense

IntegrationTestCase needs to make more sense