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

javascript/sources/Node.cc

@@ -124,6 +124,11 @@ void Node::setOverflow(int overflow)
     YGNodeStyleSetOverflow(m_node, static_cast<YGOverflow>(overflow));
 }
 
+void Node::setDisplay(int display)
+{
+    YGNodeStyleSetDisplay(m_node, static_cast<YGDisplay>(display));
+}
+
 void Node::setFlex(double flex)
 {
     YGNodeStyleSetFlex(m_node, flex);
@@ -279,6 +284,11 @@ int Node::getOverflow(void) const
     return YGNodeStyleGetOverflow(m_node);
 }
 
+int Node::getDisplay(void) const
+{
+    return YGNodeStyleGetDisplay(m_node);
+}
+
 Value Node::getFlexBasis(void) const
 {
     return Value::fromYGValue(YGNodeStyleGetFlexBasis(m_node));