Add Score to PercolateResponse

When Percolating with a query, size and trackscores=true, the raw
response contains a score, but the PercolateResponse class does not.
This is now fixed.

Author: mikelazell

src/Nest/Domain/Responses/PercolateResponse.cs

@@ -64,7 +64,9 @@ public class PercolatorMatch
 		[JsonProperty(PropertyName = "_id")]
 		public string Id { get; set; }
 		[JsonProperty(PropertyName = "highlight")]
-		public Dictionary<string, IList<string>> Highlight { get; set; }
+        public Dictionary<string, IList<string>> Highlight { get; set; }
+        [JsonProperty(PropertyName = "_score")]
+        public double Score { get; set; }
 
 	}