Better document how to install and configure GitLab Runner
The doc site has limited information about how to install and configure a Runner.
Right now GitLab Runner has its own documentation and that's ok, but being a crucial part of GitLab CI we should see to somehow bond them together. Before using CI you must first configure a runner so this basic information we don't currently expose in the doc site.
One idea is to add the Runner documentation to doc.gitlab.com.