Add total memory to cat indices response

Closes #1349

Author: gmarz

src/Nest/Domain/Cat/CatIndicesRecord.cs

@@ -31,5 +31,8 @@ public class CatIndicesRecord : ICatRecord
 
 		[JsonProperty("status")]
 		public string Status { get; set; }
+
+		[JsonProperty("tm")]
+		public string TotalMemory { get; set; }
 	}
 }