Switch to Redis for caching

Added 3 new environment variables to support the configuration of the
Redis server (REDIS_HOST, REDIS_PORT, REDIS_DB)
Remove local database config

Local development uses environment variables for DB settings
Add `league/fractal` for Transformers
Add PhotosController and PhotoTransformer
Add temporary admin filter

The logic is currently only looking for whether there is a currently
authenticated user, however this is temporary logic (until the site is
open for registration)
Add PhotosController to routes.php