Summarize what changed inbetween two runs

[ghostwords]

This compares blocked and cookieblocked base domains. Blocking different subdomains of the same base domain is not reported.

Example output from a 500 site run comparing master and the navigator.sendBeacon branch:

Closes EFForg/privacybadger#1019. We can open followup issues/PRs as needed.

[ghostwords]

Would be nice to get these emailed from scheduled runs eventually.

[bcyphers]

These requirements are installed inside the docker image, and validate.py is run outside of it. We can either add a separate requirements file to install dependencies for the outer script, or we could run validate.py inside Docker.

[ghostwords]

Are there any downsides to running it inside Docker? We'd still be able to run it by itself manually on arbitrary result files I presume.

[bcyphers]

Inside Docker is fine, I think, though it will split some of the logic out of runscan.sh. Update Dockerfile to copy validate.py and results.json into the docker container, then have docker-entry.sh call this script after it runs the crawler.