Css auto again

I'm kind-of-re-opening pull request at https://github.com/pyjs/pyjs/pull/761

You said, that you agree but you think that it's no way to go and let's start discussion. I started (tried to): https://groups.google.com/forum/?fromgroups=#!searchin/pyjs-users/autocss/pyjs-users/JKJW8MVqipQ/axEjoNcM6h8J - nobody interested in discussing. 

However, I think that change is small enough, but very useful. I agree, embedding etc.. but so far we're not embedding but we use .css anyways - so why not facilitate it?