Deletion of scss files

Because the library django-libsass isn't supported in Debian, I removed
at the moment the use of SASS for the stylesheet. I updated the
requirements.txt file accordingly.
Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>

django/requirements.txt

 Django==1.11
 django-compressor==2.2
 mysqlclient==1.3.12
-django-libsass==0.7

django/static/css/allgo.scss → django/static/css/allgo.css

@@ -3,8 +3,6 @@
   src: url(/static/fonts/Offside-Regular.ttf);
 }
 
-$navbar_bg_color: #3399cc;
-
 /*
  * Common
  */
@@ -17,7 +15,7 @@ html {
  * Header
  */
 header {
-  background-color: $navbar_bg_color;
+  background-color: #3399cc;
   border-bottom: 1px solid rgb(110, 110, 100);
   margin-bottom: 3em;
 }

django/templates/base.html

@@ -13,7 +13,7 @@
 
     <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
     {% compress css %}
-      <link rel="stylesheet" type="text/x-scss"  href="{% static 'css/allgo.scss' %}" media="all" charset="utf-8">
+      <link rel="stylesheet" type="text/css"  href="{% static 'css/allgo.css' %}" media="all" charset="utf-8">
     {% endcompress %}
 
   </head>