Add compute_input_csv functionality for masspay
Merge branch 'master' into masspay
Allow masspay script to be used non-interactively

I needed this change in order to run under foreman with environment
configuration piped in from heroku config -s.
Add username to masspay.py output
Fix bug where we were calculating tips wrong
Don't masspay unless they're due money
Fix exchange not for Gittip log
Merge branch 'master' into masspay
Merge pull request #1625 from gittip/masspay

Here's a script to manage MassPay