Don't check for montague.app_factory before defining how it works.

That's irresponsible.
Added a fake paste.server_factory and paste.server_runner using webtest's TestApp.
Added an adapter system for the different kinds of PasteDeploy entry points, now supporting server entry points.
Make the test apps properly return bytestrings (so WebTest's linter is happy).
Fix the Windows test errors (hopefully).