Fix minor typo

I've just started playing around with this module and noticed a tiny typo.

Looking forward to working more with this!

Author: forslund

README.md

@@ -65,7 +65,7 @@ session = Session.Builder() \
     .user_pass("Username", "Password") \
     .create()
 
-aceess_token = session.tokens().get("playlist-read")
+access_token = session.tokens().get("playlist-read")
 ```
 
 ### Get Music Stream