get version from manifest file

assets/js/config.js

@@ -1,8 +1,11 @@
+/* global chrome */
+//jshint esnext:true
+
 var config = {
     // Extension name
     name: 'WakaTime',
     // Extension version
-    version: '1.0.0',
+    version: chrome.app.getDetails().version,
     // Time for idle state of the browser
     // The user is considered idle if there was
     // no activity in the browser for x seconds