swift 4.1 support

Author: AlexShubin

Sources/Differentiator/SectionModel.swift

@@ -37,7 +37,12 @@ extension SectionModel
 }
 
 extension SectionModel
-    : Equatable where Section: Equatable, ItemType: Equatable {}
+    : Equatable where Section: Equatable, ItemType: Equatable {
+    public static func == (lhs: SectionModel, rhs: SectionModel) -> Bool {
+        return lhs.model == rhs.model
+            && lhs.items == rhs.items
+    }
+}
 
 extension SectionModel {
     public init(original: SectionModel<Section, Item>, items: [Item]) {