Return value 'ok' has been removed in v1.x

http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/_return_values.html
Store version of node we are connected to

Depending on the version of the node we are talking to the API endpoints
change so we need to know this.
Node API response renamed 'hostname' to 'host'
Update endpoints for nodes to restful versions
Update endpoints for cluster state to restful versions
Merge branch 'es-v1'