Update enoent and eperm error handling.
Update custom error example to use error event.
Update all tests.

To use the error event.
Remove obsolete error method.
Allow error handling pass through.

So that error listeners may intercept only certain errors and pass
others through to the default error handler.
Improve error test executables.
Add example executable for uncaught listeners.
Add example of listening for specific error.
Merge branch 'feature/errors' into develop
Remove obsolete information from the readme.