Updated asizeof.py from Pympler
Updated asizeof.py from Pympler

Replace asizeof.py with a version with fixes by Pympler authors,
including support for Python 3.8

spacetelescope/asv,qwhelan/asv,qwhelan/asv,airspeed-velocity/asv,airspeed-velocity/asv,spacetelescope/asv,airspeed-velocity/asv,spacetelescope/asv,qwhelan/asv,qwhelan/asv,spacetelescope/asv,airspeed-velocity/asv