UX: add line break before time for post navigator

Example:

- with year:

![screen shot 2014-08-30 at 16 25 06](https://cloud.githubusercontent.com/assets/5732281/4098751/fbdf49ea-3034-11e4-837b-69a05ca040e3.png)

- without year:

![screen shot 2014-08-30 at 16 24 08](https://cloud.githubusercontent.com/assets/5732281/4098750/fbdeace2-3034-11e4-98b7-fffdcd7cf01f.png)