Set up Heroku review apps (#1155)
Set up Heroku review apps (#1155)

This will allow us to create a review app for a pull request. A review app is a transient deploy of Shields with a unique URI. We can use it to interactively test new PRs without needing to run the branch locally.

Review apps would be especially useful, in conjunction with something like Netlify (#960), to test issues affecting SVG badge rendering on different browsers (#1132).

For the review app to be helpful for layout purposes, we're going to need Verdana on the CI machine. The font there is not measuring text correctly.
badges/shields,badges/shields,freezy-sk/shields,badges/shields,freezy-sk/shields