[20180730192707] Service Init, Rack Update Logs, and Bug Fixes

Rack update logs now display when using --wait on any rack-related command (e.g. convox rack update or convox rack params set)

An init: attribute has been added to services in convox.yml to specify that you would like Docker to provide a pid1 init process for zombie reaping, etc. This obviates the need for things like tini in your Docker image.