Added a (one-to-many) mapping between genes and transcripts.
Added a (one-to-many) mapping between genes and transcripts.

theoryno3/pygr,RitwikGupta/pygr,RitwikGupta/pygr,cjlee112/pygr,GenDataPro/pygr,cjlee112/pygr,GenDataPro/pygr,theoryno3/pygr,theoryno3/pygr,cjlee112/pygr,RitwikGupta/pygr,cjlee112/pygr,GenDataPro/pygr