Create a new token kind "id" and use it for css id's (surprise)

This is something that has been bugging me for a little bit. While I can understand the use of `constant`, I think `id` should be correct token.

In tandem with this, I'm curious about changing the result of `type` to `tag` for css selectors. It would make sense in conjunction with HTML and create consistent output. Think of `input[type="text"]` and `<input type="text">`. Right now the css scanner sees `input` as a `type` and the html scanner see's it as `tag`. Should they really be tokenized differently? 

What do you think?