[doc] added comments to pathnameOnly block.

lib/node-http-proxy/proxy-table.js

@@ -183,16 +183,25 @@ ProxyTable.prototype.getProxyLocation = function (req) {
   else if (this.pathnameOnly === true) {
     var target = req.url;
     for (var i in this.routes) {
-        var route = this.routes[i];
-        if (target.match(route.source.regexp)) {
-            req.url = url.format(target.replace(route.source.regexp, ''));
-            return {
-              protocol: route.target.url.protocol.replace(':', ''),
-              host: route.target.url.hostname,
-              port: route.target.url.port
-                || (this.target.https ? 443 : 80)
-            };
-        }
+      var route = this.routes[i];
+      // 
+      // If we are matching pathname only, we remove the matched pattern.
+      // 
+      // IE /wiki/heartbeat
+      // is redirected to
+      // /heartbeat
+      //
+      // for the route "/wiki" : "127.0.0.1:8020"
+      //
+      if (target.match(route.source.regexp)) {
+        req.url = url.format(target.replace(route.source.regexp, ''));
+        return {
+          protocol: route.target.url.protocol.replace(':', ''),
+          host: route.target.url.hostname,
+          port: route.target.url.port
+            || (this.target.https ? 443 : 80)
+        };
+      }
     }
 
   }