fix test that only worked due to site overwrites
use Inline::Perl5's use instead of calling run
refactor the {en,de}crypt methods

Calls the methods off the Perl 5 object directly instead of using sub
wrappers
refactor Digest::SHA code

call from Perl 5 directly instead of using a wrapper sub

move random_bytes wrapper sub to within its own method; no point
initialising that code when it is not going to be used
want to replace the randombytes code with a direct P5 call but can't
at the moment as malformed utf8 kills rakudo
add FIXME reminder for later