BUG: negative timedeltas not printing correctly
ENH: timedelta ops with other timedelta fixed to produce timedeltas

BUG: fixed timedelta (in nanops.py) to work with min/max....abs still not working
BUG: issue with timedelta64 and numpy 1.6.1 (used on travis), fixed by using views
BUG: fixed .abs on Series with a timedelta (partial fix for 2957)