Don't rely on Node.js global object

If `global` is used and handlebars is compiled for browser
usage without a Node.js `global` polyfill, handlebars
fails with a `global is undefined` error.

Fixes #1593

lib/handlebars/no-conflict.js

@@ -1,6 +1,6 @@
 export default function(Handlebars) {
   /* istanbul ignore next */
-  let root = typeof global !== 'undefined' ? global : window,
+  let root = typeof global !== 'undefined' ? global : window, // eslint-disable-line no-undef
     $Handlebars = root.Handlebars;
   /* istanbul ignore next */
   Handlebars.noConflict = function() {