KAZOO-2617: Maintenance for modb rollup
KAZOO-2617: move prev_next_year to util module
KAZOO-2617: update usage of prev_year_month
KAZOO-2617: refactor deleting modb maintenance task
KAZOO-2617: function to split account modb into account id, year, and month
KAZOO-2617: update formatting and usage of prev_year_month
KAZOO-2617: fix running eunit tests
KAZOO-2617: move split_account_mod to kazoo_modb_util and update refs
KAZOO-2617: find prev year/month from account mod, and create prev
account mod from current account mod
Merge pull request #390 from 2600hz/KAZOO-2617

KAZOO-2617: Maintenance for modb rollup