Ensure _.noConflict operates on root and not context.

lodash.src.js

@@ -738,7 +738,7 @@
     var objToString = objectProto.toString;
 
     /** Used to restore the original `_` reference in `_.noConflict`. */
-    var oldDash = context._;
+    var oldDash = root._;
 
     /** Used to detect if a method is native. */
     var reIsNative = RegExp('^' +
@@ -11558,7 +11558,7 @@
      * var lodash = _.noConflict();
      */
     function noConflict() {
-      context._ = oldDash;
+      root._ = oldDash;
       return this;
     }