Add support for space-between and space-around on align-content

Summary:
Adds the two missing alignments ```space-between``` and ```space-around``` for ```align-content``` . Those values are a noop on ```align-items``` in order to prevent a breaking changes for an additional enum.

Fix #229
Closes https://github.com/facebook/yoga/pull/364

Reviewed By: gkassabli

Differential Revision: D4528561

Pulled By: emilsjolander

fbshipit-source-id: ea6291b6dd22cef05d9eec03893250d50371236e

javascript/sources/YGEnums.js

@@ -9,13 +9,15 @@
 
 module.exports = {
 
-  ALIGN_COUNT: 6,
+  ALIGN_COUNT: 8,
   ALIGN_AUTO: 0,
   ALIGN_FLEX_START: 1,
   ALIGN_CENTER: 2,
   ALIGN_FLEX_END: 3,
   ALIGN_STRETCH: 4,
   ALIGN_BASELINE: 5,
+  ALIGN_SPACE_BETWEEN: 6,
+  ALIGN_SPACE_AROUND: 7,
 
   DIMENSION_COUNT: 2,
   DIMENSION_WIDTH: 0,