Alternate Scheme Support for Client

I wanted to use the client with SSL and found DNode very difficult to extend so I added the support directly.  The parsing of the scheme argument to the connect method is a bit odd, but was need to maintain compatibility with existing calls.

The new Connection class is simply to perform buffered IO on the stream as required by various wrapper streams, but leave the raw IO enabled for UDP (and TCP just to change as little as possible).

The use case for these changes is to have a client connect over SSL to a server wrapped with stunnel.  Cheers.