Update grunt.js with 'use strict' to support latest version of grunt

Author: RedWolves

grunt.js

@@ -1,6 +1,8 @@
 /*jshint node:true */
 module.exports = function( grunt ) {
 
+"use strict";
+
 var entryFiles = grunt.file.expandFiles( "entries/*.xml" );
 
 grunt.loadNpmTasks( "grunt-clean" );