Fix for MiniProfiler#337

Evidently the individual properties of JsonSerializerSettings are coalesced up to the default. I absolutely do not agree with this moving-target approach of n settings that may impact any consumer. In netstandard2.1 when BCL APIs for JSON re-appear this problem set should go away.

src/MiniProfiler.Shared/Internal/ExtensionMethods.cs

@@ -3,6 +3,7 @@
 using System;
 using System.Collections.Generic;
 using Newtonsoft.Json;
+using Newtonsoft.Json.Serialization;
 
 namespace StackExchange.Profiling.Internal
 {
@@ -77,13 +78,15 @@ public static string ToJson(this List<Guid> guids)
 
         private static readonly JsonSerializerSettings defaultSettings = new JsonSerializerSettings
         {
-            NullValueHandling = NullValueHandling.Ignore
+            NullValueHandling = NullValueHandling.Ignore,
+            ContractResolver = new DefaultContractResolver()
         };
 
         private static readonly JsonSerializerSettings htmlEscapeSettings = new JsonSerializerSettings
         {
             StringEscapeHandling = StringEscapeHandling.EscapeHtml,
-            NullValueHandling = NullValueHandling.Ignore
+            NullValueHandling = NullValueHandling.Ignore,
+            ContractResolver = new DefaultContractResolver()
         };
 
         /// <summary>