Style refresh

On top of #152 

A few new stuff, mainly as I didn't have internet :

 - ~~--no-cache option~~
 - --localfile to serve file from cwd and subpath (for test purpose mainly when no internet)
 - add font awesome v4 (not same class name that v3, so not compatible with current .twitter .github class tht can be use in live notebook). I want to use it to change Notebook Home and view on github by icons.
 - Use headroomjs. Title bar slide up when scrolling down and reappear if scrolling up. Nice on mobile where there is not much room.
 - ~~gzip=True on tornado to send contend as gzip if it is on accepted encoding. @rgbkrk how would gzip work with load balancers ?~~