Release a new build as part of version bump

We can automate a few more steps of the release process when running npm-version:

Run tests before a new release (using preversion script) - depends on Introduce acceptance tests #9
Run build as part of version bump (using version script)
Create an annotated tag with "commit changes" (as a template for GitHub Releases)
- May need to prevent npm-version from creating a lightweight tag with --no-git-tag-version

Related to #36

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