Tag build releases

After [adding support for bumping builds](https://github.com/darsain/grunt-bumpup/pull/7), it would be nice to tag those builds. This captures the build metadata like [node-semver does](https://github.com/isaacs/node-semver/blob/master/semver.js#L91-L97) and skips validation on whether the new version is higher than the highest tag if your version includes build metadata.

I also added a boilerplate editorconfig file since it was mentioned in the [contributing doc](https://github.com/darsain/grunt-tagrelease/blob/master/CONTRIBUTING.md) but not in the repo.