Embed item data into web request
Use generators to stream web requests
Add JSON-API tests
JSON API responds with embedded items

This effectively removes the "album_ids" and "item_ids" keys from the responses
of `/item/` and `/album/`, respectively. Instead there are "albums" and "items" keys,
respectively that contain a list of JSON representations for all albums and
items.
Merge branch 'embedded_items_generators'