Make compatible with atom-text-editor shadow DOM

As discussed in our latest [blog post](http://blog.atom.io/2014/11/18/avoiding-style-pollution-with-the-shadow-dom.html), we'll be transitioning Atom's text editor to use the shadow DOM to avoid accidental styling conflicts. Since you have a really popular syntax theme, I thought I'd save you the trouble of reading through our [upgrade guide](https://atom.io/docs/v0.147.0/upgrading/upgrading-your-syntax-theme) and just make the changes for you. Please check to make sure everything works just in case I missed something specific to your theme, but this should be straightforward. Thanks!
@nathansobo `:host[mini]`??