Respond to Oscar's review comments.
Respond to Oscar's review comments.

In particular, this adds retrying to the infiniteStream, stringOf, and
stringOfN combinators. It also slightly optimizes the loop conditions
on buildableOfN, removes lazy from most arbitrary definitions, and
cleans up a few other things.

This commit does appear to have made some benchmarks slower, although
it's possible my machine is just more busy than it was. I've also
added a few more benchmarks.

rickynils/scalacheck