Support vcfTabix tracks from track-hubs.
Support vcfTabix tracks from track-hubs.

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