Revert "ENH: Upgrading for Split. Downgrading for Python 2.7"

This reverts commit feaa42e229cf01683f863d1990beaa39435b6520.

It seems more viable to run the tournament under Python 3 and the
agents as Python 2.
tournament: update location
BF: decode Popen output as utf-8
ENH: add --interactive option

The new default is non-interactive, as this seems to be the common
case.
UT: Small cleanup
BF: fix argument passing
ENH: create a new directory for each game

Output will be stored in dumpstore-00, dumpstore-01, and so on.
UT: clean up argparse formatting
ENH: use better subprocess invocation
UT: simplify a bit more
BF: do not treat non-empty stderr as error

sklrearn generates a warning on stderr, but this does not
mean that anything is wrong.
Merge pull request #268 from ASPP/python3-again

Python3 again