Ensure TC breakage pings #allennlp-alerts about allennlp-hub

[brendan-ai2]

@schmmd, could you comment on this when you get a chance?

[brendan-ai2]

Michael got back to me directly. Thanks, @schmmd!

These settings are available under the build itself. For instance, on http://build.allennlp.org click "Hub Master" (under "AllenNLP Hub"). There will be a row of tabs including "Overview", "History", Change Log", "Issue Log", etc. At the end there is "WebHooks". Click that. You'll likely then want to "Add build WebHooks" or "Edit build WebHooks". One annoyance is that we can't easily edit the hook templates. For now that's not needed, but see http://build.allennlp.org/webhooks/templates.html. That page has additional information about how to edit them if we eventually need to.

I've added a hook that alerts the first time the "Hub Master" build either is broken or is fixed.