Support GitHub Service Hooks

It would be nice to be able to support github service hooks. I have written this which we have been using for a while:

https://gist.github.com/1296623

If you'd be interested in getting something like this into your tree, that would be awesome. Currently we use it to show commit updates on all of our projects, and its great because its pretty instantaneous. I know you have the same features planned for Announce, so maybe something like this could be integrated into Announce.pm with an option to use postbacks, or poll.

Start with the linked GitHub service-hook gist and inspect Announce.pm, which the issue identifies as a possible integration point. Compare the requested postback and polling approaches with the module's existing behavior and define the supported hook flow and completion criteria before changing code.

Written by the indexing model from the issue text.