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.