using `yield from` in Python 3.3
Revert "force everything to longs for Python 2.x support on 32-bit machines"

This reverts commit a21ff40e154d9365929f7ffc08574abda5510cfb.

This is pointless because there is no long() in python 3.x. Switching to Python 3.x only now.
Merge branch 'python33'
pure Python 3.3 now