Adding SocketIO handshake data to service call parameters

This is related to #44, #48 and #32 adding SocketIO handshake data as the service parameters like:

```js
app.configure(feathers.socketio(function(io) {
  io.set('authorization', function (handshake, callback) {
    handshake.feathers.user = { name: 'David' };
  });
}));
```

With something like:

```js
app.use('todos', {
  create: function(data, params, callback) {
    // When called via SocketIO:
    params.user // -> { name: 'David' }
  }
});