Underscore + lowercase all keys

osu.Game/IO/Serialization/KeyContractResolver.cs

@@ -0,0 +1,16 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using Humanizer;
+using Newtonsoft.Json.Serialization;
+
+namespace osu.Game.IO.Serialization
+{
+    public class KeyContractResolver : DefaultContractResolver
+    {
+        protected override string ResolvePropertyName(string propertyName)
+        {
+            return propertyName.Underscore();
+        }
+    }
+}