add support for the Dialer
I cannot build shapeshifter lib using this PR https://github.com/OperatorFoundation/shapeshifter-transports/pull/7 and the current shapeshifter library. Starting with this commit https://github.com/OperatorFoundation/shapeshifter-transports/commit/25a3b35b95a256298174407765f316b01aaa4941 the transports seem to have a slightly different architecture now, passing a proxy.Dialer during instantiation of NewObfs4Client