Keep arrowheads always in view.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Cleanup DraggableHTMLFeatures.js.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Fix error when viewing nt & aa at edge of refseq.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>