Skip supervisord if no Procfile is present in app.
Change post-release to fail on pipefail and debug on DOKKU_TRACE
Merge pull request #10 from kleinmann/feature/skip-if-no-procfile

Skip supervisord if no Procfile is present in app.
Add Procfile and SCALE to .gitignore
Clean up whitespace
Allow setting SCALE file in deployed app, optionally overriden at server level.
Install supervisor only if it's not already installed.

This should speed up app pushes if you add supervisor to the default base image.
If it's already there then we skip the apt-get update/install for it.
Thanks to @michaelshobbs for the idea and initial PR.
merge from upstream