RedisList/RedisPersister: wrong-type key reported as IndexError; bytearray stored as int list #12

Deferred from the review of #11 (both minor, no data corruption): (1) del/assignment on a key holding a Redis string surfaces as 'index out of range' IndexError instead of a wrong-type error; check the key type in the ResponseError handler. (2) pre-existing: RedisPersister[k] = bytearray(...) / memoryview is treated as an Iterable and stored as a list of ints instead of bytes; treat them as bytes-like.