Updated gemspec for 0.2.4 release.
Updated gemspec for 0.2.4 release.

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