Fixed extra margin on Navbar buttons.

docs/assets/css/bootstrap.css

@@ -2926,7 +2926,7 @@ input[type="submit"].btn.btn-mini {
   margin-top: 5px;
 }
 .navbar .btn-group .btn {
-  margin-top: 0;
+  margin: 0;
 }
 .navbar-form {
   margin-bottom: 0;

less/navbar.less

@@ -74,7 +74,7 @@
     .navbarVerticalAlign(30px); // Vertically center in navbar
   }
   .btn-group .btn {
-    margin-top: 0; // then undo the margin here so we don't accidentally double it
+    margin: 0; // then undo the margin here so we don't accidentally double it
   }
 }