Improve layout of social links on fronts

- only show first link on mobile
- give some space on desktop
- prevent labels wrapping if there's too little space

![screen shot 2014-12-11 at 13 21 19](https://cloud.githubusercontent.com/assets/867233/5394787/704660b6-8139-11e4-83b7-43fb6dd63cb4.png)

![screen shot 2014-12-11 at 13 21 37](https://cloud.githubusercontent.com/assets/867233/5394790/744e5790-8139-11e4-8f63-fd4b12e55b30.png)

![screen shot 2014-12-11 at 13 22 08](https://cloud.githubusercontent.com/assets/867233/5394793/77a580c6-8139-11e4-9c11-afbe1d2251e3.png)

http://www.browserstack.com/screenshots/f6c6bb5c3f712328cbc346dc98ecc5ad99036e41