Added property display: flex and none

Summary:
Fix #241 and successor for #302

Added new property ```display``` with ```YGDisplayFlex``` and ```YGDisplayNone```. Allows to hide nodes from the layout without the need to remove it from the DOM.
Closes https://github.com/facebook/yoga/pull/369

Reviewed By: astreet

Differential Revision: D4501141

Pulled By: emilsjolander

fbshipit-source-id: 0dfeee381f6d1e4bbba81926126b83dd7abab9d6

enums.py

@@ -52,6 +52,10 @@ ENUMS = {
         'Relative',
         'Absolute',
     ],
+    'Display': [
+        'Flex',
+        'None',
+    ],
     'Wrap': [
         'NoWrap',
         'Wrap',