Update delete endpoints to return True if successful.

If the operation isn't successful, the API returns an error code,
which raises an OpenPhotoError exception.

openphoto/api_tag.py

@@ -20,10 +20,14 @@ class ApiTag:
         return Tag(self._client, result)
 
     def delete(self, tag, **kwds):
-        """ Delete a tag """
+        """
+        Delete a tag.
+        Returns True if successful.
+        Raises an OpenPhotoError if not.
+        """
         if not isinstance(tag, Tag):
             tag = Tag(self._client, {"id": tag})
-        tag.delete(**kwds)
+        return tag.delete(**kwds)
 
     def update(self, tag, **kwds):
         """ Update a tag """