ref(docs): rewrite coding standards doc as a PR checklist
ref(docs): rewrite coding standards doc as a PR checklist

The "coding standards" document needed an update for go, our
most prevalent implementation language. It was also verbose and
a bit rambling as it had grown over time, so this attempts
to condense and focus it as a simpler checklist to follow.

deis/workflow,deis/workflow,deis/workflow