six: fix tuple assignment in method signature for py3
six: __future__ headers
cleanup: import of hashlib.md5
six: relative imports for compat and py3compat
six: use urljoin, urlquote, urldefrag from six.moves
six: use PY2, PY3 from six, __nonzero__/__bool__ compatibility
six: unicode --> text_type
six: basestring --> string_types
six: long --> long_type
minor cleanup
six: term.py done