Seed with RFC4122 v4 UUIDs

Results seem much more random now, especially when sampling multiple times via a
loop, wherein many samples can happen with the same timestamp.

However, this does slow down shuffling and sampling, but as far as I am
concerned this is better than having weak randomness. An eventual goal might be
to allow the user to specify their own seed, that way they're in charge of UUID
generation instead of us.
Release 1.1.0