os.py: do not import gevent.socket

since gevent.os is imported in __init__.py this makes gevent.socket imported in __init__.py which was never the intention.
use integer_types #38
psycopg2_pool.py: use integer_types #38
baseserver.py: use integer_types
core.ppyx: use integer_types
subprocess: types.StringTypes -> string_types #38
subprocess.py: avoid reinitilization of rawlink()
Use xrange from gevent.hub
Fix Queue -> queue, refs #38.
Merge pull request #352 from surfly/pr344

Py3-related random fixes
update util/pyflakes.py

the subprocess.py warning was actually legit and was fixed in 47f1c3d581e98834224bdd28e8afe03e7cc16fae
Use six.xrange in tests.
Merge pull request #357 from fantix/xrange

Use six.xrange in tests.
Handle renaming of "thread" to "_thread" in PY3
Merge pull request #360 from fantix/thread_renaming

Handle renaming of "thread" to "_thread" in PY3
travis: On Python3 use python3-version of pep8 #38

Previously pep8 and pyflakes were installed using the default system Python.
This changes 'make travis' to use the current Python version for those scripts as well.
This affects pep8, at least: on Python3 it complains about space in `print (...)`.
Replaced print with print_function from __future__, refs #38.
socket.py: pep8 fix on python3 #38
test__all__.py: pep8 fix on python3 #38
util/pyflakes.py: do not ignore errors, py3&py2.6

- do not swallow syntax errors
- make pyflakes.py py3-compatible #38
- run using specific version of python (previously pyflakes from the default python
  was used, which caused it to ignore py3-specific and py2.6-specific syntax errors