Fixes to request method test.

Since we're stubbing the request, the test is actually just asserting that ```@method = env['REQUEST_METHOD']```. Since the test is trying to test against the ```methodoverride``` middleware,    we should test it against an actual request. However, Rack is already [covering this scenario](https://github.com/rack/rack/blob/6829a8a0f416ea49a18f1e3e532ed1ece24e9ea4/test/spec_methodoverride.rb#L19) so it should be fine for us to remove this test.