Adds synonyms to ElasticSearch 

This is an initial pass at a WordNet recipe. The required format for the WordNet database file (Prolog) is not included in any ruby gems, therefore the latest synonyms set from WordNet 3.1 is included. 

- Adds WordNet syn lookup to Searchkick via monkeypatch

Roadmap:
- Ability to add custom synonyms (using current searchkick_synonyms filter). 
- Support additional synonym lookups 
- Refine and release a recipe for Chef