use seek(0) instead of reset()

The BytesIO class seems not to have a reset().
py3 string type
py3 int types
fix use of xrange, now using six
remove unused import
remove unused import
make the magic a byte immediately
make the empty string and empty byte
indexing into a byte in python3 does a struct unpack, wtf?
strip bytes, not strings
encode the magic format and user_codec
zlib compress and decompress accept only bytes, not strings
use wb for good measure, not sure if required
fix foobared integer division, dumbass
disable tests, 'cause they is takin' FOEVA!