[ASCornerLayoutSpec] New layout spec class for declarative corner element layout. (#657)

* Add new layout spec class with snapshot testing. Update examples and CHANGELOG.md

* Code review updates.

* Open curly bracket in a new line.

examples/LayoutSpecExamples/Sample/OverviewViewController.m

@@ -1,11 +1,18 @@
 //
 //  OverviewViewController.m
-//  Sample
+//  Texture
 //
 //  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
 //  This source code is licensed under the BSD-style license found in the
-//  LICENSE file in the root directory of this source tree. An additional grant
-//  of patent rights can be found in the PATENTS file in the same directory.
+//  LICENSE file in the /ASDK-Licenses directory of this source tree. An additional
+//  grant of patent rights can be found in the PATENTS file in the same directory.
+//
+//  Modifications to this file made after 4/13/2017 are: Copyright (c) 2017-present,
+//  Pinterest, Inc.  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
 //
 
 #import "OverviewViewController.h"
@@ -37,7 +44,10 @@
     _layoutExamples = @[[HeaderWithRightAndLeftItems class],
                         [PhotoWithInsetTextOverlay class],
                         [PhotoWithOutsetIconOverlay class],
-                        [FlexibleSeparatorSurroundingContent class]];
+                        [FlexibleSeparatorSurroundingContent class],
+                        [CornerLayoutExample class],
+                        [UserProfileSample class]
+                        ];
   }
   
   return self;