Use random_compat to provide the default source of randomness

[IMSoP]

Per #11, there is now a note about using a better source of randomness if possible, and a "PHP 7" generator which uses the crypto-safe random_int function.

However, if you add a composer dependency for paragonie/random_compat, you can make random_int the default source on all the versions of PHP you support, and that library will automatically polyfill it with the best source available.

[hackzilla]

interesting. I will have to read up on this library.