Replace Urllib3 method_whitelist with allowed_methods (#638)

* Replace method_whitelist with allowed_methods

* Add ChangeLog Entry

* update requests to 2.25 and six to 1.15

spotipy/client.py

@@ -194,7 +194,7 @@ class Spotify(object):
             total=self.retries,
             connect=None,
             read=False,
-            method_whitelist=frozenset(['GET', 'POST', 'PUT', 'DELETE']),
+            allowed_methods=frozenset(['GET', 'POST', 'PUT', 'DELETE']),
             status=self.status_retries,
             backoff_factor=self.backoff_factor,
             status_forcelist=self.status_forcelist)