Use css for scroll positionning

- Better rendering on scroll on pages with a left block
(- It removes the warning on Firefox about scroll positionning)

kfet/static/kfet/css/index.css

@@ -134,6 +134,13 @@ textarea {
     padding:0;
 }
 
+@media (min-width: 768px) {
+    .col-content-left {
+        position: sticky;
+        top:50px;
+    }
+}
+
 .content-left-top {
     background:#fff;
     padding:10px 30px;

kfet/static/kfet/js/kfet.js

@@ -1,14 +1,4 @@
 $(document).ready(function() {
-    $(window).scroll(function() {
-        if ($(window).width() >= 768 && $(this).scrollTop() > 72.6) {
-            $('.col-content-left').css({'position':'fixed', 'top':'50px'});
-            $('.col-content-right').addClass('col-sm-offset-4 col-md-offset-3');
-        } else {
-            $('.col-content-left').css({'position':'relative', 'top':'0'});
-            $('.col-content-right').removeClass('col-sm-offset-4 col-md-offset-3');
-        }
-    });
-
     if (typeof Cookies !== 'undefined') {
         // Retrieving csrf token
         csrftoken = Cookies.get('csrftoken');