Merge pull request #359 from fantix/bool_nonzero

Added __bool__ for PY3 next to __nonzero__.
fix reraise on py3

based on #362 by @fantix
fix pyflakes check on py3

and ignore gevent/util_py2.py
psycopg2_pool.py: fix pyflakes on PY3
fix pyflakes warnings on PY3
test__issue6.py: fix on PY3
fix pyflakes warning in test__select.py on PY3

Thanks to @fantix for original patch.
test__os.py: buffer/memoryview fix on PY3

thanks to @fantix for original patch.
Merge pull request #397 from surfly/pr365

py3-related fixes
replace unicode with text_type
test__subprocess.py: do not reference 'file' (PY3)
concurrent_download.py: update for py3
initial impl for socket/ssl for python3 #38
Merge pull request #398 from surfly/socket_python3_r2

initial impl for socket/ssl for python3 #38
fix urllib/urllib2/urlparse renamings in PY3 #38

Close #384.
Refs #38, fix an encoding issue in gevent.core for PY3
Fix a issue in PY3 that print_exception() fails if value is None, #38
Fix absolute import issue in core.ppyx in PY3, refs #38
Fix metaclass issue in PY3, refs #38.
fileobject module