Remove forcing HWA layer by default

Some components force a HWA layer by default. I think it's better to do it case by case so this PR removes it.

I think originally it got added because some components got used inside a Flow in the Den Demo? /cc @romancortes? In that case it could be added only to the app's style.css or if it's necessary in all Flows, it could be moved only inside Flow, like:

```css
.montage-Flow .digit-Button {
    -webkit-transform: translate3d(0,0,0);
    -moz-transform: translate3d(0,0,0);
    -ms-transform: translate3d(0,0,0);
    transform: translate3d(0,0,0);
}
```

Might also be worth looking into the `will-change` property: http://dev.w3.org/csswg/css-will-change/ Still pretty new, but it should eventually replace this zero transform hack.