Allow bytearrays to be stored as BLOBs

Fixes #50.

The idea's fairly simply; `Vector{UInt8}`s get stored directly into BLOBS, any other object gets wrapped in a `Serialization` object, serialized then stored as a BLOB. When they're deserialized the Array gets returned unchanged unless the deserialized value is a `Serialization` in which case the object which the `Serialization` holds gets returned.

Obviously the array could happen to match a `Serialization` even when if hasn't been serialized but I think this is such an unlikely corner case that it shouldn't matter too much.