This is preparatory work towards adding a Topic model.
We plan to use the local variable name as 'topic' for
the Topic model objects.
Currently, we use *topic as the local variable name for
topic names.
We rename local variables of the form *topic to *topic_name
so that we don't need to think about type collisions in
individual code paths where we might want to talk about both
Topic objects and strings for the topic name.
Since FIXTURE_DIR_NAME is the name of the folder that contains the view
and tests modules of the webhook and another folder called "fixtures" that
store the fixtures, it is more appropriate to call it WEBHOOK_DIR_NAME,
especially when we want to refer to the view module using this variable.
Prakhar Pratyush
PIG208
Anders Kaseorg
Adam Birds