change up the z-indexing and add some popover/twipsy content to the test modal on the js docs to help avoid future bugs

lib/dropdowns.less

@@ -27,7 +27,7 @@
 .dropdown-menu {
   position: absolute;
   top: 40px;
-  z-index: @zindexDropdowns;
+  z-index: @zindexDropdown;
   float: left;
   display: none; // none by default, but block on "open" of the menu
   min-width: 160px;

lib/modals.less

@@ -7,7 +7,7 @@
   right: 0;
   bottom: 0;
   left: 0;
-  z-index: @zindexPopover;
+  z-index: @zindexModalBackdrop;
   background-color: @black;
   // Fade for backdrop
   &.fade { opacity: 0; }
@@ -22,7 +22,7 @@
   position: fixed;
   top: 50%;
   left: 50%;
-  z-index: 11000;
+  z-index: @zindexModal;
   max-height: 500px;
   overflow: auto;
   width: 560px;

lib/variables.less

@@ -49,11 +49,12 @@
 
 // Z-INDEX
 // -------
-@zindexDropdowns:     1000;
-@zindexTwipsy:        1000;
-@zindexFixedNavbar:   1010;
-@zindexPopover:       1020;
-@zindexModal:         1030;
+@zindexDropdown:        1000;
+@zindexFixedNavbar:     1010;
+@zindexModalBackdrop:   1020;
+@zindexModal:           1030;
+@zindexPopover:         1040;
+@zindexTwipsy:          1050;
 
 
 // THEME VARIABLES