fix dropdown vars and make hover state be link color again, add gradient to dropdown link hovers, fix caret positions and active states on nav tabs, tweak nav link padding

remove popoverarrows mixin, relegate code to tooltips and popvers since we only used them once each; this fixes the problem of broken tooltips in 2.1

use variablef or wells background-color, update docs for glyphicons license mention, update popovers to remove that thick border and make them look mo betta

implement ie7 fluid tests and semantic.gs IE7 hack for rounding in ie7; not perfect, but mostly solid

massive update to customize page to include all the new variables (and ensure they're being used in the .less files)

fix the font-family var by using inherit instead of empty string, fix font-weight in docs for jumbotron