Enhancement: add cluster health

[faxm0dem]

It would be extremely helpful to have health stats. My python-fu being very weak, it might take a while before I do this

$ curl 0:9200/_cluster/health\?pretty
{
  "cluster_name" : "elasticsearch",
  "status" : "green",
  "timed_out" : false,
  "number_of_nodes" : 11,
  "number_of_data_nodes" : 9,
  "active_primary_shards" : 3148,
  "active_shards" : 8000,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 0,
  "number_of_pending_tasks" : 0
}