Bump to v0.3.1

I was stupidly too eager with calling `npm publish`. I wasn't even
done, and it wasn't even intended to published. But now, we're stuck
with version 0.3.1 instead of 0.3.0. Bummer. Do note; v0.3.1 does not
have any bug fixes. It's just a number bump for beauracracy's sake.
Some updates to HISTORY.md.