Body padding-top use BS' SCSS variable

app/assets/stylesheets/bootstrap-variables.scss

@@ -358,7 +358,7 @@ $grid-float-breakpoint: 992px !default; // $screen-md-min
 //##
 
 // Basics of a navbar
-// $navbar-height:                    50px
+$navbar-height: 50px;
 // $navbar-margin-bottom:             $line-height-computed
 // $navbar-border-radius:             $border-radius-base
 // $navbar-padding-horizontal:        floor(($grid-gutter-width / 2))

app/assets/stylesheets/home.scss

+@import "bootstrap-variables";
+
 body {
-  margin-top: 50px;
+  margin-top: $navbar-height;
   background-color: white;
   background-image : none;
 }

app/assets/stylesheets/new_styles/_base.scss

 body {
-  margin-top: 50px;
+  margin-top: $navbar-height;
   padding : none;
 
   &.lock {