message: fix link in README.md to feathers-socketio API docs
diff: This provider exposes [Feathers](http://feathersjs.com) services through a [Socket.io](http://socket.io/) real-time API. It is compatible with Feathers 1.x and 2.x.
  -__Note:__ For the full API documentation go to [feathersjs.com/docs/providers.html](http://feathersjs.com/docs/providers.html).
  +__Note:__ For the full API documentation go to [http://docs.feathersjs.com/real-time/socket-io.html](http://docs.feathersjs.com/real-time/socket-io.html).
  ## Quick example
  