Fixed parsing error on ES <= 1.5 introduced by the change in #1403

Author: gmarz

src/Nest/Resolvers/Converters/Aggregations/AggregationConverter.cs

@@ -242,7 +242,19 @@ private IAggregation GetExtendedStatsAggregation(StatsMetric statsMetric, JsonRe
 				reader.Read();
 				reader.Read();
 			}
-
+			while (reader.TokenType != JsonToken.EndObject && (reader.Value as string).Contains("_as_string"))
+			{
+				// std_deviation_bounds is an object, so we need to skip its properties
+				if ((reader.Value as string).Equals("std_deviation_bounds_as_string"))
+				{
+					reader.Read();
+					reader.Read();
+					reader.Read();
+					reader.Read();
+				}
+				reader.Read();
+				reader.Read();
+			}
 			return extendedStatsMetric;
 		}