Added an Composer file.
Added abstract pay gateway class.
Added an WordPress pay core statuses class.
Removed folder tree.
Added an abstract gateway config class.
Updated to the new abstract Pronamic_WP_Pay_GatewayConfig class.
Added public id and mode vars to make it work correct for the Pronamic iDEAL plugin.
Added abstract gateway config factory class.
Added missing 'abstract'.
The get_config() function should no longer be static.
Added an XML Security class to filter XML values.
Added license.
Updated Composer JSON file.
Added Pronamic as author.
Added PHP requirement.
Changed license to 'GPL'.
Added Grunt for some tasks.