Renamed some of the case class parameters. When I introduced the FrameworkMessageEvent I accidentally used "ID" instead of "Id". Normally, this wouldn't be an issue. But since the case classes are directly serialized to JSON with property names the same as the case class parameters it makes sense to remain consistent.
Merge pull request #246 from Shopify/event-case-class-property-names

Renamed some of the MarathonEvent case class parameters (*ID -> *Id)