Add proposed fragment changes (#93)

* Add proposed fragment changes

* Use explicit JSXFragment node instead of flags in JSXElement

* Remove JSXOpeningFragment and JSXClosingFragment from authoritative spec

* Make fragment syntax tokens more explicit

* Make wording less awkward

AST.md

@@ -126,17 +126,43 @@ interface JSXText <: Node {
 JSX Element
 -----------
 
-Finally, JSX element itself consists of opening element, list of children and optional closing element:
+JSX element consists of opening element, list of children and optional closing element:
 
 ```js
 interface JSXElement <: Expression {
     type: "JSXElement";
     openingElement: JSXOpeningElement;
-    children: [ JSXText | JSXExpressionContainer | JSXSpreadChild | JSXElement ];
+    children: [ JSXText | JSXExpressionContainer | JSXSpreadChild | JSXElement | JSXFragment ];
     closingElement: JSXClosingElement | null;
 }
 ```
 
+JSX Fragment
+------------
+
+JSX fragment consists of an opening fragment, list of children, and closing fragment:
+
+```js
+interface JSXFragment <: Expression {
+    type: "JSXFragment";
+    openingFragment: JSXOpeningFragment;
+    children: [ JSXText | JSXExpressionContainer | JSXSpreadChild | JSXElement | JSXFragment ];
+    closingFragment: JSXClosingFragment;
+}
+```
+
+```js
+interface JSXOpeningFragment <: Node {
+    type: "JSXOpeningFragment";
+}
+```
+
+```js
+interface JSXClosingFragment <: Node {
+    type: "JSXClosingFragment";
+}
+```
+
 Tools that work with JSX AST
 ----------------------------
 

README.md

@@ -39,6 +39,7 @@ _JSX extends the PrimaryExpression in the [ECMAScript 6th Edition (ECMA-262)](ht
 PrimaryExpression :
 
 - JSXElement
+- JSXFragment
 
 __Elements__
 
@@ -60,6 +61,10 @@ JSXClosingElement :
 
 - `<` `/` JSXElementName `>`
 
+JSXFragment :
+
+- `<` `>` JSXChildren<sub>opt</sub> `<` `/` `>`
+
 JSXElementName :
 
 - JSXIdentifier