cum-mean

Added a word to calculate cumulative mean.

Signed-off-by: lorynj <lorynj@gmail.com>
when-negative / when-positive

Convenience combinators to encapsulate testing numbers for being negative or positive, followed by call to a true quotation.

Signed-off-by: lorynj <lorynj@gmail.com>
math.combinators: fix help-lint errors.
io.streams.random: slightly faster.
Revert "math.extras: change to <clumps> to match other moving- words."

This reverts commit 4c3d15e01a89a3383e77192ebcf969c2a17e7aa8.