Create integration tests

[janisz]

Right now we have only synthetic tests that check how marathon-consul behave when it gets specific event form Marathon and how it interacts with Marathon and Consul then. Before merging commit or releasing we go thru manual testing but we don't have prepared test cases.

We need set of integration test that will launch Mesos, Marathon, Consul and marathon-consul and try to deploy, change, delete tasks/apps/groups on Marathon and see the result in Consul.

We need to prepare:

1. Multiplatform environment to run integration tests (we can use https://github.com/dankraw/marathon-consul-playground)
2. Integration tests (If we use Vagrant then this could be just golang test that will launch vagrant and m-c and perform rest calls to marathon and check effect in consul)