Update README.md

Fix link to rule definitions for adblock setting. src: https://github.com/WPO-Foundation/webpagetest/blob/master/LICENSE

Author: polarbirke

README.md

@@ -453,7 +453,7 @@ wpt.runTest(script, function(err, data) {
 * **tsViewConfigs**: _String_, configs to use when submitting results to tsviewdb (for private instances that have integrated with tsviewdb)
 * **affinity**: _String_, string to hash test to a specific test agent. tester will be picked by index among available testers
 * **priority**: _Number_, change test priority (0-9) [enforced by API key, otherwise 5]
-* **blockAds**: _Boolean_, block ads defined by adblockrules.org
+* **blockAds**: _Boolean_, block ads defined by http://adblockplus.org
 * **continuousVideoCapture**: _Boolean_, capture video continuously (unstable/experimental, may cause tests to fail)
 * **forceSpdy3**: _Boolean_, force SPDY version 3 (Chrome only)
 * **forceSoftwareRendering**: _Boolean_, force software rendering, disable GPU acceleration (Chrome only)