add additional binder for ASDisplayNode

Example/Tests/ASDisplayNode+RxSpec.swift

@@ -20,6 +20,7 @@ class ASDisplayNode_RxExtensionSpec: QuickSpec {
             let node1 = ASDisplayNode()
             let node2 = ASDisplayNode()
             let node3 = ASDisplayNode()
+            let node4 = ASDisplayNode()
 
             beforeEach {
                 node1.rx.width.onNext(ASDimension(unit: .points, value: 17.0))
@@ -31,6 +32,10 @@ class ASDisplayNode_RxExtensionSpec: QuickSpec {
                 node2.rx.maxHeight.onNext(ASDimension(unit: .points, value: 20.0))
 
                 node3.rx.preferredSize.onNext(CGSize(width: 40.0, height: 40.0))
+
+                node4.rx.backgroundColor.onNext(.red)
+                node4.rx.alpha.onNext(0.3)
+                node4.rx.isUserInteractionEnabled.onNext(false)
             }
 
             it("should has correct width") {
@@ -60,6 +65,18 @@ class ASDisplayNode_RxExtensionSpec: QuickSpec {
             it("should has correct preferredSize") {
                 expect(node3.style.preferredSize).to(equal(CGSize(width: 40.0, height: 40.0)))
             }
+
+            it("should has correct backgroundColor") {
+                expect(node4.backgroundColor).to(equal(.red))
+            }
+
+            it("should has correct alpha") {
+                expect(node4.alpha).to(equal(0.3))
+            }
+
+            it("should has correct isUserInteractionEnabled") {
+                expect(node4.isUserInteractionEnabled).to(equal(false))
+            }
         }
     }
 }

RxCocoa-Texture/Classes/ASDisplayNode+Rx.swift

@@ -11,6 +11,18 @@ import RxCocoa
 import UIKit
 
 extension Reactive where Base: ASDisplayNode {
+
+    public var alpha: ASBinder<CGFloat> {
+        return ASBinder(self.base) { node, alpha in
+            node.alpha = alpha
+        }
+    }
+
+    public var backgroundColor: ASBinder<UIColor?> {
+        return ASBinder(self.base) { node, backgroundColor in
+            node.backgroundColor = backgroundColor
+        }
+    }
 
     public var didLoad: Observable<Void> {
 
@@ -25,6 +37,12 @@ extension Reactive where Base: ASDisplayNode {
             node.isHidden = isHidden
         }
     }
+
+    public var isUserInteractionEnabled: ASBinder<Bool> {
+        return ASBinder(self.base) { node, isUserInteractionEnabled in
+            node.isUserInteractionEnabled = isUserInteractionEnabled
+        }
+    }
 
     public var setNeedsLayout: Binder<Void> {