Remove the `Makefile`, make `setup.py` retrieve the `.pb` files from release

[juanjux]

Doesn't make sense to have a Makefile when we have a setup.py file, also, we could remove the .pb files that were added to avoid a dependency on protoc from the pip package.

• Move the functionality of the Makefile to the setup.py.
• A --release switch should be added to setup.py to generate the .pb files.
• The travis build should install protoc and call --release before the pip install.
• The normal build called by pip install should check if the pb files are generated and if not, retrieve the right release zip from github an extract the files from there before install.