The python:2-onbuild Docker image is used to build a site image that
contains pelican and related tools that are used to build the site. This
repository will be mounted into the container as a volume so that local
changes can be compiled into and viewed as the site.

* `build_site.sh` will produce a compiled dev site in output/
* `dev.sh start` will start an autoreloading pelican/HTTP server
combination on host port 8000 and `dev.sh stop` will stop its container.