Started removing close from the public API.

It's the only place the user gets a reference to a connection, what are
they going to do with it?

Next steps: make Conn a private type.
Unexported all the extra stuff.
Removed the Closed function on the server.

Unexported various things.

* feature-noclose:
  Unexported all the extra stuff.
  Started removing close from the public API.
v0.3.1

* develop:
  Unexported all the extra stuff.
  Started removing close from the public API.