line-height for headers

Hi @pothibo,
I was reading your blog on a small resolution and was kind of annoyed by the line height on headers.

before: http://imgur.com/umnMFhV,sjLkqzs#1
after: http://imgur.com/umnMFhV,sjLkqzs

Cheers
Merge pull request #55 from mickey/patch-1

line-height for headers