Add back 'use strict' statements

Author: XhmikosR

Gruntfile.js

@@ -6,6 +6,8 @@
  * Licensed under the MIT license.
  */
 
+'use strict';
+
 module.exports = function(grunt) {
   // Project configuration.
   grunt.initConfig({

tasks/build-contrib.js

@@ -6,6 +6,8 @@
  * Licensed under the MIT license.
  */
 
+'use strict';
+
 module.exports = function(grunt) {
   grunt.registerTask('build-contrib', ['contrib-ci', 'contrib-core']);
 };

tasks/contrib-ci.js

@@ -6,6 +6,8 @@
  * Licensed under the MIT license.
  */
 
+'use strict';
+
 module.exports = function(grunt) {
   grunt.registerTask('contrib-ci', 'Normalizes AppVeyor and Travis CI configs.', skipIfExists => {
     skipIfExists = skipIfExists === 'skipIfExists';

tasks/contrib-core.js

@@ -6,6 +6,8 @@
  * Licensed under the MIT license.
  */
 
+'use strict';
+
 module.exports = function(grunt) {
   // Add custom template delimiters.
   grunt.template.addDelimiters('build-contrib', '{%', '%}');