Linting and starting to use Tox

[agjohnson]

This is a example of some improved linting and testing configuration, thoughts are welcome.

This is an example of linting using Prospector, which is a wrapper around a number of tools -- including flake8 and pylint. It includes a configuration that will set a low bar to getting back to linting code, and is configurable by strictness profile -- which is something we can increase when we start to clean things up more.

Output of a run here:
https://travis-ci.org/rtfd/readthedocs.org/builds/71619840

This also starts to use tox, as suggested by @destroyerofbuilds, which seems like an easy way to at least combine our testing, linting, and doc creation test commands into one tool, instead of one-off shell scripts. It makes for more reproducible tests as well, handling virtualenv creation.

This also fixes a bug on dict ordering in a test case.

[hutson]

I think, based on depending on requitements.txt that all commands are already executed with {toxinidir} as the working directory, making the inclusion of it in your paths redundant.

[agjohnson]

Explicit is better than implicit here.

[ericholscher]

👍 on this -- we should fix all the errors before merging though, perhaps in another PR on top?

[agjohnson]

I'll rebase this up and add some docs. I'll leave the runtests.sh for now, but the docs will reflect running tox locally. I'll open up some tickets against this as well, so some of these issues can be followed up on.

[agjohnson]

Docs added, this should be ready to go if it looks good.

@ericholscher I added some follow up tickets to address linting and enabling them with travis. Safe to run test suite this way for now and follow up work on other PRs without blocking getting this merged.

[ericholscher]

Ship it!