Making BSseqTstat and BSseqStat inherit from GRanges instead of hasGRanges has significant benefits #158

Hi @kasperdanielhansen,

Right now BSseqTstat and BSseqStat inherit from hasGRanges instead of simply inheriting from GRanges. IIRC this design decision was made a long time ago but I'm not sure what the reason for this choice was.

FWIW it seems that simply inheriting from GRanges has significant benefits over the hasGRanges solution. Note that making that change is relatively straightforward. I'm submitting a PR in case you're interested. See #157.

Let me know if I'm missing something.

Thanks,
H.