upgrade to elasticsearch 0.90.1.

Key facts :

- 0.90.1 release is based on Lucene 4.3
- Upgrading from 0.20 requires a full cluster restart.
- Since 0.90 regexp are supported
Merge pull request #14 from ramtej/feature/elasticsearch.upgrade.0.90.1

Indexing ElasticSearch: upgrade to elasticsearch 0.90.1.