Merge pull request #2831 from jgonggrijp/es3-this-fix-final

Take this from an isolated script context

underscore.js

@@ -13,7 +13,7 @@
   // instead of `window` for `WebWorker` support.
   var root = typeof self == 'object' && self.self === self && self ||
             typeof global == 'object' && global.global === global && global ||
-            this ||
+            Function('return this')() ||
             {};
 
   // Save the previous value of the `_` variable.