Rewrote tests with bats

As evidenced by the 11 prior commits, proper testing has revealed a
large number of gaps and inconsistencies in these scripts. bats is a
very capable replacement for the old test suite.

Changes to rebom and library

Rebom now acts like cat, just including a BOM in front.

The library has been updated to dump usage, version, and help messages
regardless of the quiet option (-q, --quiet). Previously, the observed
behavior depended on the order of options. Dumped messages were
processed at the time they were seen, so they would ignore a quiet
option that followed. It is better to behave consistently than to obey
the user inconsistently.

Moving gitstat into public repo

Added core README; dropped one not-so-useful script