mobile: reduce vertical space between posts, prevent title wrap

long username/title pairings should no longer wrap to two lines on mobile, instead the title will truncate using overflow:hidden; (with enough space as to not overlap long dates like "31 Jan")

![screen shot 2013-09-17 at 11 34 10 pm](https://f.cloud.github.com/assets/1681963/1162451/70c308a6-2013-11e3-81ca-4913512481dd.png)