Store app id and app secret (#55)

Author: joostlek

src/youtubeaio/youtube.py

@@ -57,6 +57,8 @@ def __init__(
         """Initialize YouTube object."""
         self.session = session
         self.session_timeout = session_timeout
+        self.app_id = app_id
+        self.app_secret = app_secret
         if auto_refresh_auth is None:
             self.auto_refresh_auth = app_id is not None and app_secret is not None
         else: