Given a url, return an :class:`.ConnectionPool` instance of its host.
This is a shortcut for not having to parse out the scheme, host, and port
of the url before creating an :class:`.ConnectionPool` instance.
:param url:
Absolute URL string that must include the scheme. Port is optional.
:param \\**kw:
Passes additional parameters to the constructor of the appropriate
:class:`.ConnectionPool`. Useful for specifying things like
timeout, maxsize, headers, etc.
Example::
>>> conn = connection_from_url('http://google.com/')
>>> r = conn.request('GET', '/')