v3.6.0

This version improves the provided happo-ci scripts (happo-ci-travis, happo-ci-circleci, and the canonical happo-ci script), making integration a little simpler which should hopefully lead to faster builds. Instead of bailing on CI runs that aren't part of a pull request, we now

• Run a single run (no comparison) when triggered on the main branch
• Run on branches that aren't (yet) pull requests. These runs include a comparison with the main branch.

Since we can now configure CI environments to run on master, fewer runs on PRs/branches will have to create the baseline report. In many cases, the baseline report will already be there.