New Interactive header layout

Introduces a new slim-line content header for the interactive template. This is to place more emphasis on the interactive content and reduce the scroll depth to content.

- Introduce social sharing at all breakpoints
- Two column layout from leftCol breakpoint

### Screenshots
![google chrome](https://cloud.githubusercontent.com/assets/80089/3399194/81ac3300-fd39-11e3-9d25-695bce6482b2.png)

![google chrome](https://cloud.githubusercontent.com/assets/80089/3399196/8336893c-fd39-11e3-920a-a9fc6964d1ba.png)

![google chrome](https://cloud.githubusercontent.com/assets/80089/3399197/84af0a00-fd39-11e3-8572-c8531d79216d.png)