add six library dependency
move urllib, urllib2, urlparse modules to six
rollback unnecessary doctest changes
add iteration and dict methods python3 compatibility with six

- remove unnecessary `dict.keys` usage
- add list wrappers for `dict.keys`
- add six.iteritems for items iteration
- add six.itervalues for values iteration
- add six.moved.zip for zip itiration
- fix next method for iterators
- fix some missprints