Create Go generator

The generators, located in `rtf/generators/`, all of them inheriting from `rtf/generators/base.py` should be able to generate the client (complete or a stub, it depends on how much complex all this becomes) in any target language from Python.

In particular, the generator in ghe `rtf/generators/go.py` should generate a complete/stub client for the Go programming language.

What to do:

- given the classes in every Python module, define python code the generates the interfaces and the implementations in Go.

The `Class`, `Func` and `Module` object defined in the `base.py` file should have all the information needed to create the draft.

In practice, every method should generate a message that the gRCP client should send to the client, in order to build a tensorflow program server side and execute it.

For details, refer to https://github.com/galeone/tfgo/issues/17