Add dynamic dropdown selectors

- I don't know if this is an acceptable solution or not, but these
dynamic dropdown selectors appear to work. I can select a podcast,
select an episode from that podcast, and successfully create a quote.

- These dropdowns need to be replaced by comboboxes that allow the user
to create a new podcast/episode if it is not already in the db.

- I'm not sure what views file the get_episodes method should be in. I
put it in quote.py for now.