Auto-create component.json from package.json

*I understand you are not interested in maintaining a json configuration file for every package manager out there. So I won't ask you to. However, without lifting a finger (other than accepting this pull request ;) you can make component authors and users very happy!*

These commits make `component.json` automatically created from the already maintained `package.json`, on every release. This enables use of underscore.js as a [component/component](https://github.com/component/component#readme), with *no extra effort* from the underscore.js team going forward.

There is already a [component/underscore](https://github.com/component/underscore) repo, making a copy of underscore.js available with a `component.json` file, but it is manually maintained and is already falling behind your releases. Rather than putting manual work into copying `underscore.js` and updating the `component.json` file there, it would be easier for everyone if the `component.json` can be made available and updated here, automatically.

If you accept this pull request, everything is automatic for every future release, and nobody has to do anything else to maintain it.

Thanks for your time.