Tornado redefines '::' to IPv6 only, so set '::' to None to get expected...

... behaviour

Closes #769

Signed-off-by: Lasse Bigum <lasse@bigum.org>
I think `[]` around the hostname only works for IPv6 addresses. I tested in Chrome with `http://[...]:80/` where `...` was either a domain name or a IPv4 address, and both ended up as Google Search.