clarifies the Mongo instructions in README

Author: drewrice2

README.md

@@ -244,14 +244,15 @@ the database collection.
 ```python
 # import PyMongo and connect to a local, running Mongo instance
 from pymongo import MongoClient
+import gdax
 mongo_client = MongoClient('mongodb://localhost:27017/')
 
 # specify the database and collection
 db = mongo_client.cryptocurrency_database
 BTC_collection = db.BTC_collection
 
 # instantiate a WebsocketClient instance, with a Mongo collection as a parameter
-wsClient = WebsocketClient(url="wss://ws-feed.gdax.com", products="BTC-USD",
+wsClient = gdax.WebsocketClient(url="wss://ws-feed.gdax.com", products="BTC-USD",
     mongo_collection=BTC_collection, should_print=False)
 wsClient.start()
 ```