Automattic/_s — pull request #374 by joshmcrty (2014-01-04 19:09:42+00:00)
Title: Use em instead of px for menu media query

Using `em` instead of `px` preserves proportions across a wider range of browsers and devices for the responsive nav menu when users zoom. See http://blog.cloudfour.com/the-ems-have-it-proportional-media-queries-ftw/