DO NOT MERGE Why DD modal styles

This is **just** the early styles for the Why DD modal. Thought it might help out a bit. @samjewell maybe you could look at adding the interaction to this tomoz?

![screen shot 2014-12-11 at 16 41 46](https://cloud.githubusercontent.com/assets/51724/5397742/c2e65928-8154-11e4-9d6f-d6e63fe2cb07.png)

Can we wrap the SVG in the <a> tag as well?

```
<a href="/direct-debit/guarantee">
        <img ng-gc-svg-injector class="svg-icon__external-link" data-src="/images/icons/share-boxed-sm.svg">
        The Direct Debit Guarantee
</a>
```