Fix wrong tracking tag when piwik is hosted in a subdirectory.

Reported in http://forum.piwik.org/read.php?2,101531

[ci skip]

plugins/CoreAdminHome/templates/jsTrackingGenerator.js

@@ -9,7 +9,8 @@
 
 $(document).ready(function() {
 	
-	var piwikHost = window.location.host;
+	var piwikHost = window.location.host,
+		piwikPath = location.pathname.substring(0, location.pathname.lastIndexOf('/'));
 	
 	// 
 	// utility methods
@@ -228,7 +229,7 @@ $(document).ready(function() {
 		result += '  _paq.push(["trackPageView"]);\n\
   _paq.push(["enableLinkTracking"]);\n\n\
   (function() {\n\
-    var u=(("https:" == document.location.protocol) ? "https" : "http") + "://' + piwikHost + '/";\n\
+    var u=(("https:" == document.location.protocol) ? "https" : "http") + "://' + piwikHost + piwikPath + '/";\n\
     _paq.push(["setTrackerUrl", u+"piwik.php"]);\n\
     _paq.push(["setSiteId", ' + JSON.stringify(idSite) + ']);\n\
     var d=document, g=d.createElement("script"), s=d.getElementsByTagName("script")[0]; g.type="text/javascript";\n\