Enable social icons to be hacked into fronts

By adding, for example,
```html
<a class="fc-container__header__social__action social__action social-icon-wrapper" data-link-name="" href="" target="_blank">
	<span class="social-icon social-icon--small social-icon--facebook">
		<i class="i-share-facebook--white i"></i>
		<span class="social-icon__label">Like</span>
	</span>
</a>
```
to the ‘On-page description’ field in the config tool. This a temporary hack to be replaced by a proper implementation.

To do so, this also adds:
- `.social-icon--small` option (which the fronts use)
- optional `.social-icon__label` element

![screen shot 2014-12-10 at 15 19 26](https://cloud.githubusercontent.com/assets/867233/5378366/7e1e78ee-8081-11e4-983e-999ab931813c.png)![screen shot 2014-12-10 at 15 18 49](https://cloud.githubusercontent.com/assets/867233/5378381/91d69b50-8081-11e4-9817-099e69bfc408.png)
![screen shot 2014-12-10 at 15 19 16](https://cloud.githubusercontent.com/assets/867233/5378385/a1698ab4-8081-11e4-8563-6ac4820727fa.png)![screen shot 2014-12-10 at 15 19 05](https://cloud.githubusercontent.com/assets/867233/5378372/844cbf00-8081-11e4-9e26-c41bcd88a20d.png)

http://www.browserstack.com/screenshots/3db00c3b86146f088fe50fe96fef1ebebf1688aa