Detail to support twitter-bootstrap-saas as generated by yeoman

Hi there and thanks for sharing grunt-express and grunt-express-example!
I used them to add to have express serve angular+twitter-bootstrap as generated by yeoman.

One thing that got in the way is the configuration of the static folders.
It turns out that making the directories browsable prevents the twitter-bootstrap with the saas flavor served from the '.tmp' to work as expected.

Here is the project where I am testing this:
https://github.com/hmalphettes/yeoman-angular-express-example

Let me know if I missed something trivial.