Properly remove test nodes when cleaning up.

Author: gdotdesign

core/source/Test/Html.mint

@@ -14,6 +14,7 @@ module Test.Html {
       document.body.appendChild(root)
       #{%testRender%}(#{node}, root)
       return new #{%testContext%}(root, () => {
+        #{%testRender%}(null, root)
         document.body.removeChild(root)
       })
     })()