Merge pull request #2036 from jnyrup/Equatable_fix

Let `EquatableOfInt` implement `IComparable<T>`

Tests/FluentAssertions.Specs/Numeric/ComparableSpecs.cs

@@ -642,7 +642,7 @@ public override int GetHashCode()
     }
 }
 
-public class EquatableOfInt
+public class EquatableOfInt : IComparable<EquatableOfInt>
 {
     public int Value { get; set; }
 
@@ -665,6 +665,9 @@ public override string ToString()
     {
         return Value.ToString(CultureInfo.InvariantCulture);
     }
+
+    int IComparable<EquatableOfInt>.CompareTo(EquatableOfInt other) =>
+        throw new NotSupportedException("This type is meant for assertions using Equals()");
 }
 
 public class ComparableOfInt : IComparable<ComparableOfInt>