Smoke as a trait, not an app anymore.

The previously called Smoke trait has been renamed to SmokeApp.
StaticAssets is a trait that provides a way to create smoke.Response from a given path.
The core of smoke does not require akka anymore.
Multiple smoke instances can be started in one app, as long as they are not running on the same ports.
Each Smoke trait as its own config that has the same structure as before.