Comment body is more legible on tablet and up

Sets the line-height a bit higher to make comments more legible.

Line-height was set to 20px on paragraphs and 22px on the rest.

Change proposed by Chris P, you can discuss with him.

## Before 

![screen shot 2013-12-02 at 10 52 14](https://f.cloud.github.com/assets/85783/1653938/d97c3b8a-5b3f-11e3-8f69-04147c6bd9ee.png)

## After

![screen shot 2013-12-02 at 10 51 55](https://f.cloud.github.com/assets/85783/1653940/dcb28124-5b3f-11e3-9ff6-a2186a3c2184.png)


![ ](http://4.bp.blogspot.com/-pJrU_3aH2zY/UpY2Uw3NsvI/AAAAAAABDys/2opGDJKWgI0/s1600/1.gif)