Update application.css.

Clean up fonts; there's no need to specify all of them in each selector since they are inherited.
Also, use the shorthand font property.
Update application.css.

* add missing fallback color
* add missing vendor prefixed property for Opera
Refactor header.html's properties.
Get rid of the unicode symbol from selector's name and use class instead of id.
Rename clearfix class.
Update qTip custom selectors.

* group common properties together
* get rid of useless `!important` declarations
Move qTip inclusion at the top so that it's clear.