Fix up debug labels accessors

Source/ConstraintDSL.swift

@@ -30,20 +30,20 @@
 
 public protocol ConstraintDSL {
     
-    var label: String? { get set }
     var target: AnyObject? { get }
     
+    func setLabel(_ value: String?)
+    func label() -> String?
+    
 }
 extension ConstraintDSL {
     
-    public var label: String? {
-        get {
+    public func setLabel(_ value: String?) {
+        objc_setAssociatedObject(self.target, &labelKey, value, .OBJC_ASSOCIATION_COPY_NONATOMIC)
+    }
+    public func label() -> String? {
         return objc_getAssociatedObject(self.target, &labelKey) as? String
     }
-        set {
-            objc_setAssociatedObject(self.target, &labelKey, newValue, .OBJC_ASSOCIATION_COPY_NONATOMIC)
-        }
-    }
     
 }
 private var labelKey: UInt8 = 0

Source/Debugging.swift

@@ -144,7 +144,7 @@ private func descriptionForObject(_ object: AnyObject) -> String {
     desc += type(of: object).description()
     
     if let object = object as? ConstraintView {
-        desc += ":\(object.snp.label ?? pointerDescription)"
+        desc += ":\(object.snp.label() ?? pointerDescription)"
     } else if let object = object as? LayoutConstraint {
         desc += ":\(object.label ?? pointerDescription)"
     } else {

Tests/Tests.swift

@@ -490,4 +490,8 @@ class SnapKitTests: XCTestCase {
     }
     #endif
     
+    func testCanSetLabel() {
+        self.container.snp.setLabel("Hello World")
+    }
+    
 }