Added hover animation with box-shadow

As requested.
Okay, so one key feature of Less is *nested rules*. This means that you can do something like (random example time!)...

```css
#header {
  color: black;
  .navigation {
    font-size: 12px;
  }
  .logo {
    width: 300px;
  }
}
```

in Less and then it will compile into the following css when built:

```css
#header {
  color: black;
}
#header .navigation {
  font-size: 12px;
}
#header .logo {
  width: 300px;
}
```

Let me take a minute and just say, THIS IS SUCH AN EPIC FEATURE. Okay, I'm done. Just had to get that out.

In any case, the tl;dr here is that you should nest the :active and :hover selectors inside the .afch-button css. See [the Less documentation](http://lesscss.org/features/#features-overview-feature-nested-rules) for more details.