Yeah, I just didn't want to rock the boat and change existing behavior here too much, and IMHO this is something that should probably be configurable.

In a worst case scenario, you maintain a public repo, and someone sends a PR to the build server with some naughty commands in the build scripts... oops.

Anyhow, I knew people were already using Janky one way, and I didn't want to mess up their workflow too much if building PRs was not what they wanted.

Also, in our shop, we use Janky to do CI builds, but we use regular jobs to handle merges to master, as they typically perform extra work.  For instance, we have a few public Nuget packages that are automated to publish.  We don't want PRs to do that, so we have standard Jenkins jobs for that.  


If you want to default these, I suggest just changing `janky.rb` and adding defaults for `JANKY_GITHUB_EVENT_TYPES`