Improve installation process via pip

[david4096]

In addition to moving to a stable version of protocol buffers, this PR attempts to improve the build process to close #745

• Generates compiled protocol buffers during setup
• Still requires protoc be installed locally
• Updates version of protocol buffers in travis
• Merge requirements.txt to python directory
• Removes process_schemas dependency on ga4gh.common to bootstrap setup
• Set protocol version in setup.py

Allows the compiled schemas to be installed using the pip interface. For example, pip install git+git://github.com/david4096/schemas.git@protobuf31 will install this branch of the schemas to your local environment.

The goal is to easily develop against development branches of multiple packages using requirements "constraints". These will direct the installer to resolve dependencies using developer provided git branches. @dcolligan @ejacox

[ejacox]

+1 It worked for me and I found it useful. I did 'pip install -r dev-requirements -c constraints.txt' in the server, which installed the schemas directly from github.

[dcolligan]

I don't like putting things in python/requirements.txt that are not dependencies of the ga4gh_schemas package. Your change will install, for instance, nose when someone tries to install ga4gh_schemas, and that doesn't seem right.

That and a couple nits I left in comments aside, this looks good.

[david4096]

Thanks @dcolligan and @andrewjesaitis. I've fixed the indentation and safely deleted the package_python directory. I also moved the tests and documentation generation related items to the dev_requirements so the base install is smaller. My hope is that this will make it much easier to develop against the schemas from python!

[dcolligan]

+1

[kozbo]

Looks good to me too +1