Add utm_referrer to the list of removed params

Closes #23

Author: jparise

README.md

@@ -20,6 +20,7 @@ The following query string parameters are stripped:
  - utm_content
  - utm_cid
  - utm_reader
+ - utm_referrer
  - utm_name
 
 This extension requires these [permissions][]:

background.js

@@ -1,4 +1,4 @@
-var utm_re = new RegExp('([\?\&](mkt_tok|(g|fb)clid|utm_(source|medium|term|campaign|content|cid|reader|name))=[^&#]+)', 'ig');
+var utm_re = new RegExp('([\?\&](mkt_tok|(g|fb)clid|utm_(source|medium|term|campaign|content|cid|reader|referrer|name))=[^&#]+)', 'ig');
 
 chrome.webRequest.onBeforeRequest.addListener(function(details) {
     var url = details.url;