download file from heroku dyno
#$ heroku help ps:copy
Copy a file from a dyno to the local filesystem
USAGE
$ heroku ps:copy FILE
OPTIONS
-a, --app=app (required) app to run command against
-d, --dyno=dyno specify the dyno to connect to
-o, --output=output the name of the output file
-r, --remote=remote git remote of app to use
DESCRIPTION
Example:
$ heroku ps:copy FILENAME --app murmuring-headland-14719