Add `discovery.type` into `elasticsearch.yml`
Add `discovery.type` into `elasticsearch.yml`

Printing `discovery.type` in the elasticsearch configuration allows the `ec2` type to be enabled
by a data bag or other configuration by means of the `aws` recipe.

Closes #67

bavardage/cookbook-elasticsearch,gouketsu/cookbook-elasticsearch,paulczar/cookbook-elasticsearch,GemHQ/cookbook-elasticsearch,zzugg/cookbook-elasticsearch,nbudin/cookbook-elasticsearch,spuder/cookbook-elasticsearch,michaeld/elasticsearch-cookbook,nbudin/cookbook-elasticsearch,nbudin/cookbook-elasticsearch,gilt/cookbook-elasticsearch,zzugg/cookbook-elasticsearch,zzugg/cookbook-elasticsearch,spuder/cookbook-elasticsearch,gilt/cookbook-elasticsearch,spuder/cookbook-elasticsearch,vacay/vcy-elasticsearch,vacay/vcy-elasticsearch,vacay/vcy-elasticsearch,gouketsu/cookbook-elasticsearch,gilt/cookbook-elasticsearch,gouketsu/cookbook-elasticsearch