Reorganize episodes and podcasts views

[danjac]

1. Episodes:

• views/bookmarks.py + urls/bookmarks.py
• views/history.py + urls/history.py
• views/player.py + urls/player.py
• views/episodes.py

2. Podcasts:

• views/subscriptions.py + urls
• views/private_feeds.py + urls
• views/podcasts.py

bookmarks:

bookmarks, add/remove bookmark

history:

history, remove_audio_log, mark complete

player:

start player, close player, player time update

episodes:

all other views currently in episodes.py

subscriptions:

subscriptions, unsubscribe, subscribe

private feeds:

private feeds, add private feed,remove private feed

podcasts:

all other views currently in podcasts.py

Tests:

Break up tests/views/test_episodes.py and tests/views/test_podcasts.py to follow same pattern as above e.g. test_bookmarks.py