made Score backward compatible

Author: Mpdreamz

src/Nest/Domain/Hit/Hit.cs

@@ -12,7 +12,7 @@ public interface IHit<out T> where T : class
 		IFieldSelection<T> Fields { get; }
 		T Source { get; }
 		string Index { get; }
-		double? Score { get; }
+		double Score { get; }
 		string Type { get; }
 		string Version { get; }
 		string Id { get; }
@@ -35,8 +35,12 @@ public class Hit<T> : IHit<T>
 		public T Source { get; internal set; }
 		[JsonProperty(PropertyName = "_index")]
 		public string Index { get; internal set; }
+		
+		//TODO in NEST 2.0 make the property itself double?
 		[JsonProperty(PropertyName = "_score")]
-		public double? Score { get; internal set; }
+		internal double? _score { get; set; }
+		public double Score { get { return _score.GetValueOrDefault(0); } }
+
 		[JsonProperty(PropertyName = "_type")]
 		public string Type { get; internal set; }
 		[JsonProperty(PropertyName = "_version")]

src/Nest/Resolvers/Converters/ConcreteTypeConverter.cs

@@ -175,7 +175,7 @@ internal static Type GetConcreteTypeUsingSelector<T>(
 			hitDynamic.Fields = sel;
 			hitDynamic.Source = d._source;
 			hitDynamic.Index = d._index;
-			hitDynamic.Score = (d._score is double) ? d._score : default(double);
+			hitDynamic._score = (d._score is double) ? d._score : default(double);
 			hitDynamic.Type = d._type;
 			hitDynamic.Version = d._version;
 			hitDynamic.Id = d._id;