remove HTTP check and TCP check from check-ping.rb. then add ping timeout option.
added the '--master-only' flag to allow checking not only master servers
Merge pull request #555 from hiroakis/modify_check-ping

Remove HTTP check mode and TCP check mode from check-ping.rb. Then add ping timeout option.
Merge pull request #561 from reverendus/check-es-cluster-status-fix

Added the '--master-only' flag to the 'check-es-cluster-status.rb' check