Allow userId to be set for setTags on user-specific tags

README.md

@@ -161,14 +161,17 @@ var setTagsOptions = {
     tags: {
         price: "1.99",
         language: "pl"
-    }
+    },
+    userId: 'user123' // required for user-specific tags
 };
 
 // this will set the device tags for the client's 'AppCode' application
 client.setTags(setTagsOptions , function(error, response) {
     ...
 });
 ```
+
+Note: `userId` is a required field when a user-specific tag(s) is being set.
 
 #### Get tags for device
 To get tags for a device from Pushwoosh:

index.js

@@ -196,6 +196,10 @@ PushwooshClient.prototype.setTags = function(options, callback) {
         }
     };
 
+    if (options.userId) {
+        body.request.userId = options.userId;
+    }
+
     client.sendRequest('setTags', body, function(error, response, body){
         if (error) {
             return callback(error);