Open up access to auto layout related code to allow extending them

Sources/iOS/Layout/Layout.swift

@@ -76,7 +76,7 @@ public extension UIView {
 
 public struct Layout {
   /// A weak reference to the constraintable.
-  weak var constraintable: Constraintable?
+  public weak var constraintable: Constraintable?
   
   /// Parent view of the view.
   var parent: UIView? {
@@ -84,7 +84,7 @@ public struct Layout {
   }
   
   /// Returns the view that is being laied out.
-  private var view: UIView? {
+  public var view: UIView? {
     var  v = constraintable as? UIView
     if #available(iOS 9.0, *), v == nil {
       v = (constraintable as? UILayoutGuide)?.owningView

Sources/iOS/Layout/LayoutAnchor.swift

@@ -39,17 +39,17 @@ extension LayoutAnchor: LayoutAnchorable { }
 
 public struct LayoutAnchor {
   /// A weak reference to the constraintable.
-  weak var constraintable: Constraintable?
+  public weak var constraintable: Constraintable?
   
   /// An array of LayoutAttribute for the view.
-  let attributes: [LayoutAttribute]
+  public let attributes: [LayoutAttribute]
   
   /**
    An initializer taking constraintable and anchor attributes.
    - Parameter view: A Constraintable.
    - Parameter attributes: An array of LayoutAtrribute.
   */
-  init(constraintable: Constraintable?, attributes: [LayoutAttribute] = []) {
+  public init(constraintable: Constraintable?, attributes: [LayoutAttribute] = []) {
     self.constraintable = constraintable
     self.attributes = attributes
   }

Sources/iOS/Layout/LayoutAttribute.swift

@@ -31,7 +31,7 @@
 import UIKit
 
 /// A typealias for NSLayoutConstraint.Attribute
-internal typealias LayoutAttribute = NSLayoutConstraint.Attribute
+public typealias LayoutAttribute = NSLayoutConstraint.Attribute
 
 internal extension Array where Element == LayoutAttribute {
   /// A LayoutAttribute array containing top and left.