Allow specific orgs to bypass credit card payment

https://trello.com/c/qhVm4brL/379-allow-special-bulk-pricing-for-organizations

* Add orgs to EXEMPT_ORGS environment variable as comma separated list
CoffeeScript: Don't complain about implicit parens
Paginate to get all of the PR comments

PR comments are returned 30 at a time. If a PR has a lot of comments then we
will generate duplicate comments, because we're not looking at all the comments.
This fix will fetch all the comments for us by paginating until the end.

* refactor the pagination to apply for user repos, org repos and comments