We should handle SIGTERM too.

A better approach to this seem to be https://github.com/stretchr/graceful however it depends on API only available to Go 1.3+ (as described in https://code.google.com/p/go/issues/detail?id=4674)
What do you think about requiring Go 1.3?

Commit 558f650 address a part of this issue, it handles waiting for requests to finish and not listening for further connections.
However we also need to:

• Stop healing and wait for current healings to finish;
• Stop queue processing and wait for current jobs to finish;
• Stop node auto scaling checks and wait for current scaling processes to finish;
• Stop log pub/sub connections to close log -f requests

Finished but forgot to reference issue in commits. :/