Graceful restarts

With this release a pause/resume functionality is introduced to the queue.

You can restart Drone gracefully with #33 by

• pausing the queue
• waiting until all running jobs completed
• restart

Or stop agents by

• pausing the queue
• waiting until all running jobs completed
• resume the queue

Use the images from Docker Hub

laszlocloud/drone-oss-08-agent:0.8.99
laszlocloud/drone-oss-08-server:0.8.99