Block level sharing style changes

Numerous changes to the styling of block level sharing across the gallery and live blog pages. This includes removing the truncation, ready to change the sharing options.

**Live site on the left, changes on the right.**

# Live blogs 
![screen shot 2014-10-28 at 18 08 48](https://cloud.githubusercontent.com/assets/2236852/4814189/4d050130-5ece-11e4-8002-b0cbb3d9fda5.png)
![screen shot 2014-10-28 at 18 09 07](https://cloud.githubusercontent.com/assets/2236852/4814194/55c433f4-5ece-11e4-8530-5ae70e779337.png)

# Galleries
Mobile lightbox:
![screen shot 2014-10-28 at 18 06 59](https://cloud.githubusercontent.com/assets/2236852/4814203/663af6aa-5ece-11e4-89b7-2632738a80d7.png)

Gallery mobile sharing overlay now has custom styles:
![screen shot 2014-10-28 at 18 07 27](https://cloud.githubusercontent.com/assets/2236852/4814217/814f84a6-5ece-11e4-8cdb-4a35661dd536.png)

Changes on tablet too:
![screen shot 2014-10-28 at 18 10 47](https://cloud.githubusercontent.com/assets/2236852/4814235/a1f2326c-5ece-11e4-89a3-e94cf212d237.png)




Extra scoping to .share-modal__link is needed for the hover states, otherwise you get all of the button hover states whenever you hover over .share-modal