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/.eslintrc.js

@@ -0,0 +1,6 @@
+module.exports = {
+  env: {
+    // Handlebars should run natively in the browser
+    node: false
+  }
+};

lib/handlebars/compiler/code-gen.js

@@ -6,9 +6,9 @@ let SourceNode;
 try {
   /* istanbul ignore next */
   if (typeof define !== 'function' || !define.amd) {
-    // We don't support this in AMD environments. For these environments, we asusme that
+    // We don't support this in AMD environments. For these environments, we assume that
     // they are running on the browser and thus have no need for the source-map library.
-    let SourceMap = require('source-map');
+    let SourceMap = require('source-map'); // eslint-disable-line no-undef
     SourceNode = SourceMap.SourceNode;
   }
 } catch (err) {

lib/handlebars/helpers/each.js

@@ -63,9 +63,9 @@ export default function(instance) {
             execIteration(i, i, i === context.length - 1);
           }
         }
-      } else if (global.Symbol && context[global.Symbol.iterator]) {
+      } else if (typeof Symbol === 'function' && context[Symbol.iterator]) {
         const newContext = [];
-        const iterator = context[global.Symbol.iterator]();
+        const iterator = context[Symbol.iterator]();
         for (let it = iterator.next(); !it.done; it = iterator.next()) {
           newContext.push(it.value);
         }

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() {

lib/index.js

@@ -1,5 +1,6 @@
 // USAGE:
 // var handlebars = require('handlebars');
+/* eslint-env node */
 /* eslint-disable no-var */
 
 // var local = handlebars.create();

lib/precompiler.js

@@ -1,3 +1,4 @@
+/* eslint-env node */
 /* eslint-disable no-console */
 import Async from 'neo-async';
 import fs from 'fs';