Fix playlist add items (#559)

* fixed uri issue in playlist_add_items

All uris were being converted to track uris
making it impossible to add episodes to playlists.

* Added tests for episode adds

also fixed creep uri so those tests no longer fail

* Fixed creep_url to match creep_uri

* revert pip version, added FIX to changelog

Co-authored-by: Paul Lamere <paull@spotify.com>

spotipy/client.py

@@ -1824,7 +1824,13 @@ class Spotify(object):
         return id
 
     def _get_uri(self, type, id):
-        return "spotify:" + type + ":" + self._get_id(type, id)
+        if self._is_uri(id):
+            return id
+        else:
+            return "spotify:" + type + ":" + self._get_id(type, id)
+
+    def _is_uri(self, uri):
+        return uri.startswith("spotify:") and len(uri.split(':')) == 3
 
     def _search_multiple_markets(self, q, limit, offset, type, markets, total):
         if total and limit > total: