Use single dropdown menu for pages
add font awesome 4.x support
make page title centered, and move menu to right
use icon for nav menu
iconify page info
add twitter share button
add share buttons
fix broken link
css and layout of nav button and tagline
optimize layout for page info and share icons
fix navbar in large and small modes
modify footer message
add helper to show last commit date of current page

commit date is obtained from git log with grit gem. write a custom
helper to show it in the page