Moved ul.breadcrumb margin to bootstrap-tweaks.css

When importing other bootstrap themes from sites like bootswatch, the
margin in default.css persists and adds a 70px margin below the header.
This change will remove that margin when users choose to use a different
bootstrap theme.

rest_framework/static/rest_framework/css/bootstrap-tweaks.css

@@ -60,6 +60,10 @@ a single block in the template.
   color: #C20000;
 }
 
+ul.breadcrumb {
+  margin: 70px 0 0 0;
+}
+
 .pagination>.disabled>a,
 .pagination>.disabled>a:hover,
 .pagination>.disabled>a:focus {

rest_framework/static/rest_framework/css/default.css

@@ -32,10 +32,6 @@ h2, h3 {
   margin-right: 1em;
 }
 
-ul.breadcrumb {
-  margin: 70px 0 0 0;
-}
-
 .breadcrumb li.active a {
   color: #777;
 }