expose the new "get_address" callback, that enables the users to patch the (host,port) resolver instead of "inet_aton", an IPv4-only & name only resolver
when establishing an SSL connection, use the ordinary connect and then upgrade the connection
add comment re IPv6
support binding the transport to socket other than IPv4 (e.g. IPv6, unix socket, ...)
add test for the "get_address" callback
update doc
Merge pull request #64 from kazuho/kazuho/refactor-address-resolution

refactor address resolution