Generate nonces within calls

[davedoesdev]

I was wondering whether sodium-plus could remove nonce as an argument to calls generate the nonces within the library.
This would prevent apps mistakenly re-using the same nonce.
The nonce would be returned along with the result, so the API would need changing.

[paragonie-security]

A higher-level library that depends on sodium-plus can easily do this. One such example is ciphersweet-js.