Add license to callCallback, return this from ImageClassifier#loadModel

Author: tmcw

src/ImageClassifier/index.js

@@ -38,6 +38,7 @@ class ImageClassifier {
 
   async loadModel() {
     this.model = await this.modelToUse.load(this.version, this.alpha);
+    return this;
   }
 
   async predictInternal(imgToPredict, numberOfClasses) {

src/utils/callcallback.js

@@ -1,3 +1,8 @@
+// Copyright (c) 2018 ml5
+//
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
 export default function callCallback(promise, callback) {
   return callback ? promise.then((result) => {
     callback(undefined, result);