Improved admin testability
Renamed test files

Otherwise they don't get executed. Derp.
Merge pull request #139 from tooxie/tests

Tests
Space
Wishlist: Users
Playlist tests
Playlist resource
Playlist model
Returning 204 on PUT
Added display_name to User model

This will be a random string defined by the user to show instead of the user or
id. Can be null.
Adding some constraints

If required information is missing a 400 (Bad Request) is returned.
FUCKUP
Better return codes documentation