Implement test for robonode transport layer with mocked logic

[MOZGIII]

This is sort of like unit tests for the transport layer. The idea is a follows: we take robonode warp server and run it in the tests with mocked Logic (we'd obviously need to traitify Logic there). Then we test that warp server by sending the HTTP requests and validating that requests are properly parsed, and responses are properly serialized. We also have to test the error conditions, and validate that we use proper status codes for the relevant errors.