Updating CHANGELOG.md after release 0.2.15

CHANGELOG.md

@@ -2,6 +2,18 @@
 <!--LATEST=0.2.8-->
 <!--ENTRYINSERT-->
 
+##04/11/2018
+* aws-amplify - v0.2.15
+    *Enhancement: Preserve error context when loading Cognito credentials. #577
+    *Enhancement: Increase test coverage for PubSub. #588
+    *Enhancement: Fix StorageCache configure and use InMemoryCache. #635
+    *Bug Fix: Sign out fix. #511
+    *Bug Fix: Adding Polyfill.js to fix PubSub. #588
+    *Bug Fix: Ensure credentials retrieved only once on page reload. #486
+    *Bug Fix: Fix empty object returned in componentDidMount when using Auth.currentUserInfo. #608
+    *Bug Fix: Setting authData after ConfirmSignIn
+
+
 ## 03/30/2018
 * amazon-cognito-identity-js - v2.0.3
     * Bug Fix: missing es folder in npm package