Make the burger look right

• Make burger use the 4 spans as specified by bulma docs.
• Correct the burger animation to use those 4 spans
• Color the burger white

sass/_menu.scss

@@ -11,17 +11,20 @@
 .navbar .navbar-toggle:checked {
     &+.navbar-brand .navbar-burger {
         & span:nth-child(1) {
-            -webkit-transform: translateY(5px) rotate(45deg);
-            transform: translateY(5px) rotate(45deg);
+            -webkit-transform:  rotate(45deg);
+            transform: translateY(0px) rotate(45deg);
         }
 
         & span:nth-child(2) {
             opacity: 0;
         }
-
         & span:nth-child(3) {
-            -webkit-transform: translateY(-5px) rotate(-45deg);
-            transform: translateY(-5px) rotate(-45deg);
+            opacity: 0;
+        }
+
+        & span:nth-child(4) {
+            -webkit-transform:  rotate(-45deg);
+            transform: translateY(-6px) rotate(-45deg);
         }
     }
 
@@ -73,4 +76,12 @@
   #navbar-logo > img {
     filter: saturate(0) brightness(0) invert(1);
   }
+  #navbar-logo > img:hover {
+    filter: none;
+  }
+}
+
+// FIXME: https://github.com/jgthms/bulma/issues/3757
+.navbar-burger {
+    color: white !important;
 }