use variables for padding

src/client/styles/scss/_override-bootstrap-variables.scss

@@ -79,6 +79,8 @@ $dropdown-border-radius: 0;
 
 //== card
 $card-border-radius: 0;
+$card-spacer-y: 7px;
+$card-spacer-x: 15px;
 
 //== Modals
 $modal-content-border-width: 0;

src/client/styles/scss/_override-bootstrap.scss

@@ -20,7 +20,6 @@
 }
 
 .card-header {
-  padding: 7px 15px;
   font-weight: 700;
   text-transform: none;
   border-radius: $card-border-radius;
@@ -32,7 +31,7 @@
 
 // Well (substitute Well of bootstrap3)
 .card.well {
-  padding: 7px 15px;
+  padding: $card-spacer-y $card-spacer-x;
 }
 
 // Dropdowns