Fix hamburger for topbar and offcanvas

Hi,

this PR is to fix 2 bugs :
- offcanvas text positioning next to the hamburger (removing the line-height)

before: ![offcanvas_bug](https://cloud.githubusercontent.com/assets/6872180/3183119/7a15452e-ec62-11e3-88f3-a8d75e73de0d.png)
after: ![offcanvas_fix](https://cloud.githubusercontent.com/assets/6872180/3183122/7ec365a6-ec62-11e3-9b8b-3bb310976c70.png)

- hamburger positioning in the topbar

before: 
![menu_bug](https://cloud.githubusercontent.com/assets/6872180/3183128/af6312b0-ec62-11e3-8c8f-44a1d90fd202.png)
after: 
![menu_fix](https://cloud.githubusercontent.com/assets/6872180/3183129/b84cac60-ec62-11e3-9e90-ad6137226096.png)

related issues : https://github.com/zurb/foundation/issues/5199 and https://github.com/zurb/foundation/issues/5263