Some improvements that I've made when adapting it for my use.

Hey, I like this project and I've had some fun making some improvements so I thought I'd share them. You can see them all in action here: http://codepen.io/SimeonC/pen/wsDaH.

A quick run-down of my thoughts/changes etc:

- This is better as a Class than an attribute, it is purely visual so a class makes most sense.
- Included Coffeescript, just cause I like coding in it.
- Updated the CSS to be more robust and look a lot nicer in a transition sense - added bonus I only found recently is that this has the advantage of changing the placeholder colour with .has-warning and similar.
- Placeholder moves out if changed from model, but we don't add any more watchers - uses ngModel.$formatters.

Thanks for sharing your code with us as it's a great UX concept.