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)

Awesome PNGs - soooo nice.
We might be able to compress these a bit more (and make them interlaced too) - ~30% file savings... shout me and I can PR this for you.