Avoid defaulting concurrency to "1"
Avoid defaulting concurrency to "1"

This default has the nasty tendency to cause maintenance processes
defined in Procfile (normally run as one-shots) to run amok and be
restarted continuously.

For example, if one defines the following process scaled to zero, it
would be run and restarted rapidly to negative effect without this
change:

   $ cat Procfile
   migrate: bundle exec rake db:migrate

fdr/hsup-fdr,fdr/hsup-fdr,heroku/hsup,heroku/hsup