simplify int.from_bytes(data, 'big') + other

[VladimirFokow]

Implements this comment: mikepound#3 (comment)

• replaced unnecessary int.from_bytes(data, 'big') with just data

• cube_hash is now not an int but bytes

• change naming: cube_hash to cube_id

• typo correction: get_canoincal_packing

• relevant docstring updates

[bertie2]

thanks for the typo and doc fixes, and yes I agree this is no longer relevant to call a hash since its reversible.
also even at n=9 this saves on average 1 second so will definitely add up fast, better yet it appears to even be slightly more memory efficient so should help at n>12 scale. didn't realize python implemented comparisons on bytes so well.

merging with no further changes requested, benchmarks below:

pullrequests\VladimirFokow> python .\cubes.py --no-cache 9

Hashing polycubes n=3
completed 100.00%

Generating polycubes from hash n=3
completed 100.00%

Hashing polycubes n=4
completed 100.00%

Generating polycubes from hash n=4
completed 100.00%

Hashing polycubes n=5
completed 100.00%

Generating polycubes from hash n=5
completed 100.00%

Hashing polycubes n=6
completed 100.00%

Generating polycubes from hash n=6
completed 100.00%

Hashing polycubes n=7
completed 100.00%

Hashing polycubes n=8
completed 100.00%
Generating polycubes from hash n=8
completed 100.00%

Hashing polycubes n=9
completed 100.00%

Generating polycubes from hash n=9
completed 100.00%

Found 48311 unique polycubes

Elapsed time: 58.426s

pullrequests\bertie2> python .\cubes.py --no-cache 9

Hashing polycubes n=3
completed 100.00%

Generating polycubes from hash n=3
completed 100.00%

Hashing polycubes n=4
completed 100.00%

Generating polycubes from hash n=4
completed 100.00%

Hashing polycubes n=5
completed 100.00%

Generating polycubes from hash n=5
completed 100.00%

Hashing polycubes n=6
completed 100.00%

Generating polycubes from hash n=6
completed 100.00%

Hashing polycubes n=7
completed 100.00%

Generating polycubes from hash n=7
completed 100.00%

Hashing polycubes n=8
completed 100.00%

Generating polycubes from hash n=8
completed 100.00%

Hashing polycubes n=9
completed 100.00%

Generating polycubes from hash n=9
completed 100.00%

Found 48311 unique polycubes

Elapsed time: 60.398s