Explain motivation for funjible.set-precondition-mods-only namespace
Add namespace funjible.set-precondition-always-transient-mods

For the purposes of performance comparison with the original
clojure.set (and maybe against other versions).  These versions always
use transients whenever possible, even if the collections are so small
that it might be slower to use transients.
Some code to read and begin summarizing of benchmarks