Gravity Perks (Gravity Wiz) 2.3.7

Fixed security issue.
Fixed notice generated when fetching available perks and no license key is specified.

Fixed several fatal errors that occurred when running older versions of Gravity Forms.
Fixed issue where unmet minimum requirements did not prevent GP_Plugin-based perks from initializing.
Updated minimum required version of Gravity Forms to fix fatal errors where GFAddon::meets_minimum_requirements() did not exist.

Updated licensing and updates API for significant performance improvements.