Thanks so much @amokleben for adding the differences.
I want to share my experience using 14.04 instructions on 16.04. I was able to follow the 14.04 instructions until I got to the Upstart section. Since 16.04 doesn't have Upstart, I installed it. At first it wasn't working. When I typed sudo start mattermost, it gave the following error:
start: Unable to connect to Upstart: Failed to connect to socket /com/ubuntu/upstart: Connection refused
I had to properly install Upstart (which I found by searching for this error message on google). After this change, things seemed to work properly afterwards.
But your instructions sound like they are better.