Remove v3 changelog

Author: sudonatalie

background.js

@@ -16,9 +16,3 @@ chrome.tabs.onUpdated.addListener(function (tabId, changeInfo, tab) {
 chrome.pageAction.onClicked.addListener(function (tab) {
   chrome.tabs.executeScript(null, {file: 'toggle-layout.js'});
 });
-
-chrome.runtime.onInstalled.addListener(function (details) {
-  if (details.reason ==  "update" && parseFloat(details.previousVersion) < 3) {
-    chrome.tabs.create({'url': chrome.extension.getURL('changelog/changelog.html')});
-  }
-});