Switched form layout to use flexbox

So much saner now...

![image](https://cloud.githubusercontent.com/assets/706039/3392769/4cccb884-fcb8-11e3-80a9-d1e9e66a526e.png)

Also added a little script to dynamically inject the proper form label/id for accessibility purposes.
If the input already has an ID, then it won't be overwritten. I should definitely spell this out in the docs though.

You won't be able to hard-code a 'for' attribute, since the `<label>` is created via this directive.