Changing to file level use strict statement

lib/core/InterceptorManager.js

@@ -1,7 +1,8 @@
+'use strict';
+
 var utils = require('./../utils');
 
 function InterceptorManager() {
-  'use strict';
   this.handlers = [];
 }
 
@@ -14,7 +15,6 @@ function InterceptorManager() {
  * @return {Number} An ID used to remove interceptor later
  */
 InterceptorManager.prototype.use = function (fulfilled, rejected) {
-  'use strict';
   this.handlers.push({
     fulfilled: fulfilled,
     rejected: rejected
@@ -28,7 +28,6 @@ InterceptorManager.prototype.use = function (fulfilled, rejected) {
  * @param {Number} id The ID that was returned by `use`
  */
 InterceptorManager.prototype.eject = function (id) {
-  'use strict';
   if (this.handlers[id]) {
     this.handlers[id] = null;
   }
@@ -43,7 +42,6 @@ InterceptorManager.prototype.eject = function (id) {
  * @param {Function} fn The function to call for each interceptor
  */
 InterceptorManager.prototype.forEach = function (fn) {
-  'use strict';
   utils.forEach(this.handlers, function (h) {
     if (h !== null) {
       fn(h);