Use common string case for URIInfo hostname comparison.

If a hostname in mixed case is provided as the `uri` parameter to `register_uri()`, the request will not be patched.
The issue is `urlparse.urlsplit` [1](http://docs.python.org/2/library/urlparse.html#urlparse.urlsplit), which is used to construct an URIInfo instance (`URIInfo.from_uri()`); `urlsplit` returns the hostname part in lowercase, which causes the patched and current-request URIInfos to fail matching in `fakesock.socket.sendall()`.