[WIP] Issue36 - Eureka integration

[dcaba]

I started to cover this: https://github.com/dachad/tcpgoon/issues/36

And following a tdd approach... tests are quite complete (but end to end), and main pending points are:

• complete eureka client implementation passing the integration tests
  • we are not using fargo for the client... the things we need to do are too simple, but for tests (where we register a dummy service)
• refactors / see inline notes and TODOs
• expose the functionality to the cmd
• update READMEs...

Feel free to start sharing feedback, @chadell