[Enhancement] Multi Socket Support

Adding the ability to define multiple sockets on a single route. They are defined like:

```js
Ember.Route.extend({
  socketConfigurations: [{
    url: 'ws://localhost:8080'    
  }, {
    url: 'ws://localhost:8081',
    keepSocketAlive: false,
    binaryType: 'blob'
  }]
});
```