Give YogaKitSample some love, Convert it to a Swift Project

Summary:
To date, our sample project was lacking. There is still a lot of work that can be done to improve, but, this is a step in the right direction.

Here are the changes in this commit:
1. The project is written in Swift.
2. Created new CollectionView (via [IGListKit](https://github.com/instagram/iglistkit)), making it very easy to add new examples.
3. New examples for basic layouts, and including/excluding layouts on the fly.

Here's a video!

![](https://media.giphy.com/media/l0ExcvTLa0ADdawRa/giphy.gif)
Closes https://github.com/facebook/yoga/pull/392

Reviewed By: emilsjolander

Differential Revision: D4550379

Pulled By: dshahidehpour

fbshipit-source-id: 64a07acf96c1887f1d2ad0c54971fcedb64334a0

YogaKit/YogaKitSample/Podfile.lock

@@ -1,19 +1,26 @@
 PODS:
+  - IGListKit (2.1.0):
+    - IGListKit/Default (= 2.1.0)
+  - IGListKit/Default (2.1.0):
+    - IGListKit/Diffing
+  - IGListKit/Diffing (2.1.0)
   - Yoga (1.1.0)
   - YogaKit (1.1.0):
     - Yoga (~> 1.1)
 
 DEPENDENCIES:
+  - IGListKit (~> 2.1.0)
   - YogaKit (from `../../YogaKit.podspec`)
 
 EXTERNAL SOURCES:
   YogaKit:
-    :path: "../../YogaKit.podspec"
+    :path: ../../YogaKit.podspec
 
 SPEC CHECKSUMS:
+  IGListKit: b826c68ef7a4ae1626c09d4d3e1ea7a169e6c36e
   Yoga: 0bf083b7c485b20598020dbedcea869cbe53071e
   YogaKit: 80df90de9ef2900baa111f2c93476a6f9e921385
 
-PODFILE CHECKSUM: 9db3bdea7f1b4b715ad859a449b2dc87fb6226cc
+PODFILE CHECKSUM: 216f8e7127767709e0e43f3711208d238fa5c404
 
 COCOAPODS: 1.2.0