Fixed active pill color in navigations example

src/assets/less/site/bootstrap/variables.less

@@ -121,6 +121,8 @@
 //@brand-danger:          @red;
 //@brand-info:            @blue;
 
+// Pills
+@nav-pills-active-link-hover-bg: @link-color;
 
 // Carousel
 @carousel-text-shadow:                        0 1px 0 rgba(255,255,255,0.25);