Make compatible with elasticsearch gem - version 2.0.0

I am trying to use this gem in our project however it is locked to version 1 of the elasticsearch gem

```
 forklift_etl was resolved to 1.0.8, which depends on
      elasticsearch (>= 1.0.0, ~> 1.0)
```

any idea on how large of a task it is to make this compatible for use with the elasticsearch 2.0.0 version?