This commit removes the GitLab CI cruft and adds some Circle CI config files for the site. Right now, the pipeline is really simple since our site is really simple. It is just one raw HTML page.
This may change over time if we explore other tools like Jekyll or Hugo for building and publishing a static website.
Closes #120 (closed). It is passing for an implementation, but the CI pipeline is not as integrated as I would have liked. But it works and it enables us to better catch problems before they make it to production.