remove whitespace below menubar when toolbar hidden.

closes  #7292

IPython/html/static/notebook/less/menubar.less

@@ -4,7 +4,7 b''
   .navbar {
     border-top: 1px;
     border-radius: 0px 0px @border-radius-base @border-radius-base;
-    margin-bottom: 6px;
+    margin-bottom: -1px;
   }
   
   .navbar-toggle {

IPython/html/static/notebook/less/toolbar.less

@@ -1,7 +1,7 b''
 .toolbar {
     padding: 0px;
     margin-left: -5px;
-    margin-top: -5px;
+    margin-top: 2px;
     margin-bottom: 5px;
 
     select, label {

IPython/html/static/style/style.min.css

@@ -9766,7 +9766,7 b' select[multiple].celltoolbar select {'
 #menubar .navbar {
   border-top: 1px;
   border-radius: 0px 0px 2px 2px;
-  margin-bottom: 6px;
+  margin-bottom: -1px;
 }
 #menubar .navbar-toggle {
   float: left;
@@ -10296,7 +10296,7 b' span.autosave_status {'
 .toolbar {
   padding: 0px;
   margin-left: -5px;
-  margin-top: -5px;
+  margin-top: 2px;
   margin-bottom: 5px;
   box-sizing: border-box;
   -moz-box-sizing: border-box;