Start some nav and dropdown cleanup

* Remove border-radii on top of tab dropdown menus
* Remove the .dropdown and .dropup styles and instead place  on all
* Use  on dropdown carets intead of separately applying margin with a top alignment
* Some other misc cleanup

less/dropdowns.less

@@ -2,14 +2,8 @@
 // Dropdown menus
 // --------------------------------------------------
 
-
-// Use the .menu class on any <li> element within the topbar or ul.tabs and you'll get some superfancy dropdowns
-.dropup,
-.dropdown {
-  position: relative;
-}
-.dropdown-toggle:active,
-.open .dropdown-toggle {
+// Remove the outline when :focus is triggered
+.open > a {
   outline: 0;
 }
 
@@ -19,19 +13,14 @@
   display: inline-block;
   width: 0;
   height: 0;
-  vertical-align: top;
+  margin-left: 2px;
+  vertical-align: middle;
   border-top:   4px solid #000;
   border-right: 4px solid transparent;
   border-left:  4px solid transparent;
   content: "";
 }
 
-// Place the caret
-.dropdown .caret {
-  margin-top: 8px;
-  margin-left: 2px;
-}
-
 // The dropdown menu (ul)
 // ----------------------
 .dropdown-menu {