Random number generation docs should mention ints

[alex]

https://cryptography.io/en/latest/random-numbers/ doesn't say what to do if you want an integer, instead of bytes.

[alex]

int.from_bytes(os.urandom(16), "big") is strictly speaking the right answer.

[alex]

Except python 2.6 :-(

[alex]

A fun test might be to just put the int.from_bytes() bit in teh docs and see who complains?

[wbond]

Probably everyone who is using Python 2.7 will complain also since it is 3.2+.

[alex]

@reaperhulk do you have thoughts about whether to recommend int.from_bytes (py3 only), make our int_from_bytes public, or some third option I haven't thought of.

[reaperhulk]

I'm inclined to say int.from_bytes() or int(uuid.UUID4()) ("only" 128-bit, but py2/py3)