Style folder hierarchy in headings

This makes the display of folders in the `<h1>` look like the prototype.

It alters the behaviour we’ve initially built here by only ever showing
a maximum of two levels of hierarchy (the current folders and its
parent).

app/assets/stylesheets/components/message.scss

@@ -55,3 +55,59 @@
   }
 
 }
+
+.folder-heading {
+
+  .column-main>.grid-row:first-child &.heading-medium {
+    margin-top: 18px;
+  }
+
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+
+
+  a,
+  &-folder {
+
+    display: inline-block;
+    vertical-align: top;
+    padding: 5px 0 0 60px;
+    background-repeat: no-repeat;
+    background-size: 38px auto;
+    background-position: 0 1px;
+
+  }
+
+  a {
+
+    background-image: file-url('folder-blue.svg');
+    max-width: 33%;
+    overflow: hidden;
+    text-overflow: ellipsis;
+
+  }
+
+  &-folder {
+
+    padding-left: 0;
+
+    &:first-child {
+      background-image: file-url('folder-black.svg');
+      padding-left: $gutter * 2;
+    }
+
+  }
+
+  &-separator {
+
+    display: inline-block;
+    vertical-align: top;
+    color: $secondary-text-colour;
+    padding: 5px 4px 0 5px;
+    font-weight: normal;
+
+  }
+
+
+}