Make sure that links are clickable

Because we set a padding of 50px on anchorable elements to make
sure they are not obscured by the header, we need to raise the
z-index of links so they are not obscured by these paddings.

apidoc/template/static/styles/jaguar.css

@@ -17,6 +17,10 @@ body {
   padding-top: 50px;
   margin-top: -50px;
 }
+a {
+  position: relative;
+  z-index: 1;
+}
 .navigation li {
   color: #888;
 }