change order of scss file import

on sass files override, the modification will be reflected only
in the usage after overriding. see: http://stackoverflow.com/questions/11773583/can-i-override-sass-variables-after-they-have-been-imported
add font and color sass variables
temporary comment out header and footer on the city layout file
add navbar styles
improve city page style

todo: decouple navbar in city layout
and remove nesting!