VictorOps service

Thanks to @nicky-isaacs for the original implementation and @collinvandyck for adding support for our new alert clearing feature. I made some final tweaks to explicitly enforce v2 alerts and to add more verbose output as the `state_message`.

Sample alert:

![screen shot 2014-10-16 at 10 54 56 am](https://cloud.githubusercontent.com/assets/494338/4664602/25d86eae-5545-11e4-9646-9d2b64a53348.png)