Show NEW badge next to new Jobs

This PR conditionally shows a NEW badge next to the title of Job Posts in the jobs list, if the job is 3 days old or less.

Would appreciate @berkcaputcu and @jaredphillips taking a look, been a while since I’ve worked on Rails migrations…

![screen shot 2014-03-12 at 11 54 53 am](https://f.cloud.github.com/assets/65468/2399450/aafedaf2-a9fe-11e3-9528-4ac2055602e9.png)