Adds `rx_state` to `NSButton`.

RxCocoa/OSX/NSButton+Rx.swift

@@ -20,4 +20,15 @@ extension NSButton {
     public var rx_tap: ControlEvent<Void> {
         return rx_controlEvent
     }
+
+    /**
+    Reactive wrapper for `state` property`.
+    */
+    public var rx_state: ControlProperty<Int> {
+        return rx_value(getter: { [weak self] in
+            return self?.state ?? 0
+        }, setter: { [weak self] state in
+            self?.state = state
+        })
+    }
 }

Tests/RxCocoaTests/Control+RxTests+Cocoa.swift

@@ -41,4 +41,9 @@ extension ControlTests {
         let createView: () -> NSButton = { NSButton(frame: CGRectMake(0, 0, 1, 1)) }
         ensureEventDeallocated(createView) { (view: NSButton) in view.rx_tap }
     }
+
+    func testButton_StateCompletesOnDealloc() {
+      let createView: () -> NSButton = { NSButton(frame: CGRectMake(0, 0, 1, 1)) }
+      ensureEventDeallocated(createView) { (view: NSButton) in view.rx_state }
+    }
 }