Updated signal handler signature
Fixed locale detection. Used Babel standartized tools
Changed groupon validation error format & status code passed. Needed for support IE XDR
Changed error reporting
Purged widget support. Refactored customer processing
Extracted order and cart structures into the separate mixins
Cutted out serrvice data provisioning
Changed sum calculation to aggregation expression
Renamed ticket details transfer attribute
Updated groupon payment and verification process according to the data structure changes
Expanded allowed headers list