rename call to Headers.to_list -> to_wsgi_list
fix unicode error in parse_cookie -- works both in py2 & py3
Merge pull request #329 from puzzlet/sprint/http

fix unicode error in parse_cookie -- works both in py2 & py3
Merge pull request #327 from puzzlet/sprint/datastructures

rename call to Headers.to_list -> to_wsgi_list