Update grunt.js

added "use strict" for grunt 0.3.17 lint check

Author: ronchalant

grunt.js

@@ -1,5 +1,7 @@
 module.exports = function( grunt ) {
 
+"use strict";
+
 var entryFiles = grunt.file.expandFiles( "entries/*.xml" );
 
 grunt.loadNpmTasks( "grunt-clean" );