Refactor Kit transport
Refactor tests
Remove grab option: `strip_xml_declaration`
Remove sleep method
Fix grab_xml_processing test
Refactor method of global request counter generation
Cookie support in Kit transport

--HG--
rename : test/cookies.py => test/grab_cookies.py
Add cookies/POST/headers/user-agent features to webkit transport

--HG--
rename : test/grab_simple.py => test/grab_get_request.py
rename : test/post_feature.py => test/grab_post_request.py