Drone Autoscale updated for 1.0.0-rc.1

I just updated the Drone autoscaler to work with 1.0.0-rc.1

If you are using the autoscaler with 0.8.0 please make sure you use the Docker image drone/drone:0.8.0. The latest tag is not compatible with the 0.8.0 server.

I have also published updated documentation. The only difference (in terms of configuration) is that you no longer need to provide the agent host. This value is now inferred from the server host and server proto variables. Otherwise everything is the same.