Support profiling Django 1.3+ CBVs

This allows you to profile methods on CBVs. Since everything is hanging
off of the request object it's still non-trivial to profile other
methods (e.g. get_context_data) but it's at least possible to do this::

    class MyView(TemplateView):
        …

        @devserver_profile(follow=[do_heavy_lifting])
        def get(self, request):
            …
Merge pull request #74 from acdha/cbv-profiling-support

Support profiling Django 1.3+ CBVs