Create SVG to illustrate heroku pipeline deploy workflow

We're using the heroku labs pipeline plugin:
https://devcenter.heroku.com/articles/labs-pipelines#enable-pipelines

To feel comfortable deploying (for people who aren't me), we need a good visual reference for how deploy works, including commands to push slugs through the pipeline, how envvars change between environments, and which irc #channels the testbot appears in.

Here's to how render an SVG from the project in a markdown file (thanks @rgrove!):
https://rawgithub.com/