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

yoga/YGEnums.h

@@ -13,7 +13,7 @@
 
 YG_EXTERN_C_BEGIN
 
-#define YGAlignCount 6
+#define YGAlignCount 8
 typedef YG_ENUM_BEGIN(YGAlign) {
   YGAlignAuto,
   YGAlignFlexStart,
@@ -21,6 +21,8 @@ typedef YG_ENUM_BEGIN(YGAlign) {
   YGAlignFlexEnd,
   YGAlignStretch,
   YGAlignBaseline,
+  YGAlignSpaceBetween,
+  YGAlignSpaceAround,
 } YG_ENUM_END(YGAlign);
 
 #define YGDimensionCount 2