Only using 'id' OR 'name' from pb path in datastore.Entity.save.

This was introduced in #289 and discovered while rebasing those
changes into #281.

The datastore backend fails if both 'id' and 'name' are set on
a key, so this only copies the parts of the saved pb key that
are actually set.
Merge pull request #291 from dhermes/fix-key-error-in-entity-save

Only using 'id' OR 'name' from pb path in datastore.Entity.save.
General outlook on JS regression tests.
Ditching environ module, allowing argparse to fall back to environ vars.
Local temp.
Temp stash looks good.