added support for pulling list of statements associated with a subscription
added support for pulling list of statements associated with a subscription

chase439/chargify_api_ares,elfotografo007/chargify_api_ares,wsmoak/chargify_api_ares,outstand/chargify_api_ares,chargify/chargify_api_ares,carsonreinke/chargify_api_ares