Updated middleware Providers to take Sender config, fixed wsgi CONTENT_LENGTH error

[markstuart]

I'm using raygun4py in a project where it's already used as wsgi middleware. Recently we found that some of the env vars going through to Raygun we wanted to filter out, and it seems the way to do that is via config to the RaygunSender when initialising it.

Unfortunately, only the Django middleware supports this, so I raised this PR to hopefully get the other middlewares up to the same level.

[coveralls]

Coverage increased (+0.1%) to 88.559% when pulling 2d0e4fd53767589803f0598f28d1bb83ebc2f20a on mediasuitenz:add_config_to_middleware into f65727a8cc8c6e4b089a68efcd906d6dd7080568 on MindscapeHQ:master.

[sreecodeslayer]

hey folks, any chance this can get merged and have a release I want to disable env vars from being sent on a flask app