Notify sender when tests fail

[dLobatog]

Currently tests take a long time to run. Therefore most people who send a pull request don't wait until tests have finished running, and they don't know the status of their PR, instead they think everything is fine when the tests might have failed. I suggest the prprocessor should actually ping the person in question and tell the person how to run tests locally & a link to the failures in Jenkins.

Also the PR should be set as waiting on contributor as that's the state if fixes are required.

[domcleal]

It might be easiest to do this in test-pull-requests, which if you hunt through the old commits used to actually comment rather than using the GitHub status API (I converted it).

That said, keeping it in prprocessor might be more future proof as I'd quite like to replace test-p-r with the Jenkins PR testing plugin one day.