News container design tweaks

- fake variations of the image importance (image highlighted) - already in the tool, coming soon in frontend's model
- remove some tweaks and replace them with Kat's designs decisions
- fix browser rendering issues

Before: http://m.code.dev-theguardian.com/uk-alpha

After:

## Mobile

![mobile](https://f.cloud.github.com/assets/85783/1879764/bd734906-794e-11e3-982b-5a6c0ce70474.png)


## Mobile Landscape

![mobile-landscape](https://f.cloud.github.com/assets/85783/1879766/c0b2e87e-794e-11e3-971f-2b7401322578.png)


## Tablet

![tablet](https://f.cloud.github.com/assets/85783/1880214/66025714-7955-11e3-9167-8d8041f1d96f.png)



## Desktop

![desktop](https://f.cloud.github.com/assets/85783/1879770/c75e29b8-794e-11e3-815a-f2d70d2dfd3b.png)