Add support for SVG ellipse elements.

Closes #1675

docs/docs/ref-04-tags-and-attributes.md

@@ -31,7 +31,7 @@ thead time title tr track u ul var video wbr
 The following SVG elements are supported:
 
 ```
-circle defs g line linearGradient path polygon polyline radialGradient rect
+circle defs ellipse g line linearGradient path polygon polyline radialGradient rect
 stop svg text
 ```
 

src/browser/ReactDOM.js

@@ -174,6 +174,7 @@ var ReactDOM = mapObject({
   // SVG
   circle: false,
   defs: false,
+  ellipse: false,
   g: false,
   line: false,
   linearGradient: false,

src/vendor/core/getMarkupWrap.js

@@ -37,6 +37,7 @@ var shouldWrap = {
   // they will be initialized in the wrong namespace (and will not display).
   'circle': true,
   'defs': true,
+  'ellipse': true,
   'g': true,
   'line': true,
   'linearGradient': true,
@@ -78,6 +79,7 @@ var markupWrap = {
 
   'circle': svgWrap,
   'defs': svgWrap,
+  'ellipse': svgWrap,
   'g': svgWrap,
   'line': svgWrap,
   'linearGradient': svgWrap,