Support selection of multiple tiers.
Support selection of multiple tiers.

jeffhsu3/dalliance,Traksewt/dalliance,dasmoth/dalliance,limeng12/dalliance,Traksewt/dalliance,jeffhsu3/dalliance,ENCODE-DCC/dalliance,bartcharbon/dalliance,warelab/dalliance,bartcharbon/dalliance,ENCODE-DCC/dalliance,limeng12/dalliance,dasmoth/dalliance,warelab/dalliance