Add script for building releases
Change some wording in the README
Strip everything after the "snip" line

Commit messages can contain uncommented diffs (or any other content), as
long as they occur after a special "snip" line recognized by git. This
change correctly strips out snipped text.
Sort violations by position

This makes the output a lot easier to read.
Update documentation in main.go
Add .gitignore
Update subj-no-period description to be accurate

Instead of saying "the subject should not have a period", say that it
"should not end with a period" (which is what the rule actually
enforces).
Change usage to recommend linking to commitfmt