Make clusterrunner deploy error messages more user-friendly

and also have it exit with the proper exit code. Was previously exiting
with a 0 exit code even upon failure.

Additionally, fix the async/blocking issue where the 'stop' command was
being asynchronously executed when it should have been a blocking call.
Merge pull request #4 from box/make_clusterrunner_deploy_errors_prettier

Make clusterrunner deploy error messages more user-friendly