fixed nit in readme

Author: Jon Heaton

README.md

@@ -54,7 +54,8 @@ Once you have an access token (whether via the script or from the user flow), yo
 from instagram.client import InstagramAPI
 
 access_token = "YOUR_ACCESS_TOKEN"
-api = InstagramAPI(access_token=access_token)
+client_secret = "YOUR_CLIENT_SECRET"
+api = InstagramAPI(access_token=access_token, client_secret=client_secret)
 recent_media, next_ = api.user_recent_media(user_id="userid", count=10)
 for media in recent_media:
    print media.caption.text