restored 'groups' function lost in transition to 2.8
restored 'groups' function lost in transition to 2.8

ktakagaki/breeze,chen0031/breeze,ktakagaki/breeze,scalanlp/breeze,crealytics/breeze,sheide/breeze,tjhunter/scalanlp-core,mredaelli/breeze,wstcpyt/breeze,ContentSquare/breeze,eponvert/breeze,claydonkey/breeze,cilier/breeze,calippo/breeze,nikdon/breeze,tjhunter/scalanlp-core