feat(CLI): --debug flag to output traffix

* If `--debug` is set, we will output all server communication to
  stderr. That way, we can compare our requests to what is expected by
  ush based on official docs.
* `discovery` now doesn't use the API key anymore - this is specified
   using a custom override.

Nice, we are totally ready to test and fix all API features.

Related to #70

etc/api/type-cli.yaml

@@ -29,5 +29,6 @@ cargo:
     - docopt = "*"
     - docopt_macros = "*"
     - rustc-serialize = "*"
+    - yup-hyper-mock = "*"
     - serde = ">= 0.3.0"
     - serde_macros = "*"