Integrate with Papertrail Heroku Add-on

[remeika]

We are deploying Metabase with the Heroku add-on, and would like a way to integrate paper trail logging via the Heroku Papertrail Add-on.

This add-on injects a single environment variable, PAPERTRAIL_API_TOKEN, into the application. I am not sure if this is enough information to set up Papertrail (The AWS EB deployment strategy requires injecting Papertrail hostname and port in order to set it up). But it is, this would be a really nice addition to the Heroku deployment pattern.