added class to image

[nevace]

Thanks for the library, very useful.

I've just made a small addition so classes added to the directive appear on the image element. In my case I wanted the class 'md-avatar' on it to fit nicely with angular-material. I added devDependencies to the package.json just for future forks.

Thanks,

Liam

[marchrius]

Nothing about this? Is very usefull to use a custom class for img element

[jgesser]

Please release this. I will help me too.
It should also have support to ng-class, for dynamic classes.

[cfwen]

I made the exactly same changes in my own repo, would be happy to see it merged