On the whole, it was an awesome project with immense learing experience for me, regarding both Elasticsearch and the new Drupla 8.
The module currently works for the latest Drupal 8.0.x with Search API sandbox and uses the official Elasticsearch-php library. I’ve also included a set of Search API test cases.
The project was successfully merged in the Elasticsearch Connector 8.x branch which will be its new home. I’ll keep updating the module on both project sandboxes with the changes reflected in Drupal 8 and Search API.