Enable IDE code-highlighting for bin-file

By adding the `.js`-extension to the bin-file, IDEs will
know that js code-highlighting should be applied to the
file, which makes it easier for devs to read the code.

bin/handlebars → bin/handlebars.js

@@ -111,7 +111,6 @@ delete argv._;
 
 const Precompiler = require('../dist/cjs/precompiler');
 Precompiler.loadTemplates(argv, function(err, opts) {
-
   if (err) {
     throw err;
   }

package.json

@@ -79,7 +79,7 @@
     "./runtime": "./dist/cjs/handlebars.runtime.js"
   },
   "bin": {
-    "handlebars": "bin/handlebars"
+    "handlebars": "bin/handlebars.js"
   },
   "scripts": {
     "build": "grunt build",

spec/expected/help.menu.txt

@@ -1,5 +1,5 @@
 Precompile handlebar templates.
-Usage: handlebars [template|directory]...
+Usage: handlebars.js [template|directory]...
 
 Options:
   --help               Outputs this message                                                                    [boolean]

tasks/test-bin.js

@@ -219,9 +219,9 @@ function executeBinHandlebars(...args) {
   if (os.platform() === 'win32') {
     // On Windows, the executable handlebars.js file cannot be run directly
     const nodeJs = process.argv[0];
-    return execFilesSyncUtf8(nodeJs, ['./bin/handlebars'].concat(args));
+    return execFilesSyncUtf8(nodeJs, ['./bin/handlebars.js'].concat(args));
   }
-  return execFilesSyncUtf8('./bin/handlebars', args);
+  return execFilesSyncUtf8('./bin/handlebars.js', args);
 }
 
 function execFilesSyncUtf8(command, args) {