Include pip requirement.txt in Largo

[benlk]

Running sphinx (any by extension grunt build, which wraps it) requires sphinx and related programs, which are currently managed by a requirements.txt file for pip. That file is typically contained in umbrella repositories, using the example fabfile from the deploy tools as an example.

Why is there a fabfile in the deploy tools? To take care of the requirements for the deploy tools.

Why are Largo-specific requirements included in the largo umbrella requirements.txt? Because that was probably what was easiest at the time, when all our sites were under one repository.

We should:

• create a requirements.txt for Largo that specifies what's required for this project in particular
• exclude it from the git sftp list of things that gets deployed
• make sure that we can run grunt build without errors, and change docs in largo.readthedocs.io to account for the changed location of the fabfile.
  • probably requires creating a testing-purposes virtualenv
  • create an issue to upgrade Largo and inn/deploy-tools to pipenv
• improve docs related to this

[benlk]

requirements.txt:

sphinx==1.2.3
sphinxcontrib-phpdomain==0.1.4

#1456 will remove the need for sphinx, ideally, but until then, we should ship requirements.txt in Largo.