Better vertical rhythm

Close #240

Post width is shorter to display around 80 chars max.

Before
![home](http://cl.ly/image/463X1N0L273m/Screen%20Shot%202014-10-16%20at%2011.11.14.png)
After
![home](http://cl.ly/image/0M0Z2e3X0M1g/Screen%20Shot%202014-10-16%20at%2011.11.26.png)

Before
![post header](http://cl.ly/image/1j04422O3u3g/Screen%20Shot%202014-10-16%20at%2011.11.40.png)
After
![post header](http://cl.ly/image/1N1s2u100y0L/Screen%20Shot%202014-10-16%20at%2011.11.55.png)