Display "post" instead of "posts" in "Show 1 new post"

### Before

![screen shot 2014-05-12 at 14 51 01](https://cloud.githubusercontent.com/assets/85783/2945038/84782862-d9dc-11e3-8620-7fe37e327fbf.PNG)


### After

![screen shot 2014-05-12 at 14 51 13](https://cloud.githubusercontent.com/assets/85783/2945039/875c2268-d9dc-11e3-8adc-6522783f1205.PNG)


@rich-nguyen @phamann @mattosborn I couldn't find the JS tests for this. Would love to know how to test it if you don't have time to test it yourselves.

![night-is-a-dark-time](https://cloud.githubusercontent.com/assets/85783/2946459/0cd62506-d9ec-11e3-93b4-3d36125d93ba.gif)