option to specify transcript ID's in count tables

[gktharp1]

want to be able to choose gene symbols or ensemble ID's ( gene_id )

[derrik-gratz]

I think we'd have to add a function that re-maps the transcript IDs to gene symbols and vice-versa. Our current workflow has the geneIDs replaced by the symbols in the bulk template (separate from this package). We could try leveraging the summarized experiment object at the base of DESeq objects to store multiple genenames. A lazy fix would just be to re-load the GTF back in and map them back if needed