Removed previously unused test framework in favor of tox + docker-compose version

[solarkennedy]

@kevinschoon this is me trying to finish the transition from these manual tests to the new ones.

The new tests run via travis, or locally. I think it is going to be easier for someone to run the new tests locally because it only requires having docker installed. The previous test suite required that the user already have marathon and a mesos setup with docker enabled, and a callback server available on 192.0.2.1. And of course if they don't want to run the tests, Travis will for them.

Having these tests is good, but nobody ran them as evidence of the broken appid validation logic that got into master.

I don't want an unused test suite around that nobody is running, it will rot, so I'm deleting it in this PR.
If you want test coverage on the HTTP callback functionality of marathon+marthon-python, please PR a new version of these tests that can be run in the new itest suite, and automatically via Travis. This will ensure it will stay up-to-date as things change.

[kevinschoon]

@solarkennedy I agree, the integration tests were too complicated to setup and run. I added them because I didn't want to create a PR without having some tests to run and none had previously existed. I can submit a new suite of tests in a separate PR that are easier to run.

[solarkennedy]

Don't get me wrong, I really appreciate the testing!
I'm still down for testing this feature, and I think we could also have a "unit test" suite too, were we could catch things like #50 as well. It will get better :)