Require six version 1.4.0 or later.

six.moves.urllib.parse is available since version 1.4.0.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Use six.moves.urllib.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Merge pull request #1370 from omasanori/six-version

Require six version 1.4.0 or later.
Fix HTMLParser related deprecation warnings in Py3.4
Patch docutils.io.FileInput to not use "U" mode in py3

"U" mode is redundant in py3 since "newline" argument replaces it and by default
universal newlines is enabled. As of py3.4, "U" mode triggers a deprecation warning.