• Backwards incompatible: The FlaskRedis.init_app method no longer takes
  a strict parameter. Pass this flag when creating your FlaskRedis
  instance, instead.
• Backwards incompatible: The extension will now be registered under the
  (lowercased) config prefix of the instance. The default config prefix is
  'REDIS', so unless you change that, you can still access the extension via
  app.extensions['redis'] as before.
• Backwards incompatible: The default class has been changed to
  redis.StrictRedis. You can switch back to the old redis.Redis class by
  specifying strict=False in the FlaskRedis kwargs.
• You can now pass all supported Redis keyword arguments (such as
  decode_responses) to FlaskRedis and they will be correctly passed over
  to the redis-py instance. Thanks, @giyyapan!
• Usage like redis_store['key'] = value, redis_store['key'], and
  del redis_store['key'] is now supported. Thanks, @ariscn!