based versions that are semver compatible. If a prerelease
identifier is already present we'll bump ahead by adding `.plus.`
and the number of subsequent commits. If its not, we'll bump the
patch digit and call it `alpha.0` and add the remaining `.plus.` bit.
This also changes the file names of the mpy zips to include "-mpy-"
which should help space out two potentially confusing version strings
(that of circuitpython and that of the library.)
