Add master branch alias

Hi guys,

After reading though [Igor's blog post](https://igor.io/2013/01/07/composer-versioning.html) we're trying to get as many of our dependencies on tags as we can. It would be great if you could tag a release of this bundle as we use it in a lot of our projects, but in the meantime, would you consider aliasing `dev-master` as per this PR?

Thanks,
Craig