Setting both `font-size` and `line-hight` for `.line-number` is probably a wrong idea. <img width="538" alt="screen shot 2016-01-23 at 2 22 39 pm" src="https://cloud.githubusercontent.com/assets/977697/12529548/07e95006-c1dd-11e5-9660-c78562bd7cae.png">
