modal refinements in docs and general responsiveness

less/responsive.less

@@ -56,15 +56,16 @@
   // Modals
   .modal {
     position: absolute;
-    top: 20px;
-    left: 20px;
-    right: 20px;
+    top:   10px;
+    left:  10px;
+    right: 10px;
     width: auto;
     margin: 0;
     &.fade.in { top: auto; }
   }
   .modal-header .close {
     padding: 10px;
+    margin: -10px;
   }
 
 }