Use channel subscriptions to identify Twitter keyword searches

This is achieved through WebHook callbacks in the same way as was done with the Filtrand example app.

![screen shot 2014-10-23 at 02 11 13](https://cloud.githubusercontent.com/assets/328367/4746910/a7bd7c28-5a51-11e4-927c-f57f2f237c4a.png)

See commit messages for more information.

I'm not saying you should accept this pull request. It's just a good way of highlighting how the app could be made super-generic.