check for Python 3.2

in setup.py and init

treats unsupported 3.x < 3.3 like unsupported 2.x
reset readline after running PYTHONSTARTUP

should avoid conflicts between IPython and Python completions
don't ensure_ascii in JSON messages in Session
Merge pull request #5582 from minrk/pythonstartup-readline-sad

reset readline after running PYTHONSTARTUP
Merge pull request #5500 from minrk/check-3.3

check for Python 3.2
Merge pull request #5628 from minrk/no-ensure-ascii

don't ensure_ascii in JSON messages in Session