Added basic error handling for failed shards in histogram module.

Kibana does not display feedback to the user if a search result has failed indices for the Histogram module. In my case, this was a result of the 'Default Index' for a dashboard being mis-configured to query all ES indices, instead of my logstash created indices. I found at least one other user with the same issue ( http://elasticsearch-users.115913.n3.nabble.com/error-message-in-logfile-Parse-Failure-No-mapping-found-for-timestamp-in-order-to-sort-on-td4054895.html ) . 

This patch adds basic error reporting when the Histogram module receives failed indices in the results.