This is large refactoring of websocketd app:

* Server and Handler code separated to two logical pieces
* SIGINT and SIGKILL are polished and reliable now to get to wrapped app
  when the connection is closed
* Consumer/Producer pattern for running app instead of PIPE connector
  that was there before.
Removing idea of reusable process pool.

That was implemented only for introducing mux/demux. This is now not a
good place to do that.
Polishing termination sequence.
Fixed err variable name. Updated godoc visible names and comments.
Merge pull request #86 from asergeyev/master

Server and Handler separation for libwebsocketd