* fix(subscriptions): round up months
* fix(subscriptions): resub improvements
Don't allow negative extraMonths; flatten new Dates to YYYYMMDD
* fix(subscriptions): remove resub Gems exploit
Also standardizes some uses of new Date() to remove potential race condition oddities.
* fix(subscriptions): bump consecutive months...
...even if the user didn't log in then, if subscription has been continuous through that period
* test(subscriptions): cover fix cases
Also refactor: use constant for YYYY-MM format
* refactor(subscriptions): don't stringify moments