bytes pr draft

[jessekrubin]

Currently copy-pasta-ed the pyo3-bytes impl and will PR into there once I get thoughts from @kylebarron.

Something is super screwy in the decode function

Tests are in ry/tests/test_bytes.py and a a bit crude

Key Additions:

• slicing in __getItem__
• hex function
• attempt at decode
• the __repr__ string returns a string that should eval to an equal Bytes obj (i dont think it is technically identical to how python's builtin bytes do stringifying but it works (see tests))

[kylebarron]

Thanks! I'm about to go on vacation for a few days, so I probably won't have time to review this until Wednesday

[jessekrubin]

Happy vacation!