Added conditional compilation for ISet

IPA.Loader/Config/Stores/CollectionConverter.cs

@@ -102,6 +102,7 @@ namespace IPA.Config.Stores.Converters
         public CollectionConverter() : base(new TConverter()) { }
     }
 
+#if NET4
     /// <summary>
     /// A <see cref="CollectionConverter{T, TCollection}"/> for an <see cref="ISet{T}"/>, creating a <see cref="HashSet{T}"/> when deserializing.
     /// </summary>
@@ -145,6 +146,7 @@ namespace IPA.Config.Stores.Converters
         /// <seealso cref="ISetConverter{T}.ISetConverter(ValueConverter{T})"/>
         public ISetConverter() : base(new TConverter()) { }
     }
+#endif
 
     /// <summary>
     /// A <see cref="CollectionConverter{T, TCollection}"/> for a <see cref="List{T}"/>.