Elasticsearch upgrade 2.1

Author: wyhw

README.md

@@ -10,7 +10,8 @@ Versions
 
 IK version | ES version
 -----------|-----------
-master | 2.0.0 -> master
+master | 2.1.0 -> master
+1.5.1 | 2.1.0
 1.5.0 | 2.0.0
 1.4.1 | 1.7.2
 1.4.0 | 1.6.0