Minos-apigateway

* Add support for external Authentication systems based on tokens.
* Remove `minos-apigateway-common` dependency.

* Add support to `CORS`.

* Support auto discoverable endpoints.
* Handle requests to unavailable microservices.
* Improve request forwarding to microservices.
* Fix bug related with unnecessary `json` casting.

* Bugfix.

* First release on PyPI.