BUG/OFMT: fix spurious tuple repring of bytes types in python 3
CLN: clean up _is_sequence
ENH/CLN: add string and binary types compat object
Merge pull request #4456 from cpcloud/fix-py3-bytes-repr

BUG/OFMT: fix repring of python3 bytes objects
BUG: series timedelta arithmetic was not being converted to ns
TST/ENH: add test for subtraction
TST: add timedelta conversion in older numpy