Add responsiveness for footer. Update gulpjs, package.json and bootstrap sass

static/assets/bootstrap/sass/_breadcrumb.sass

@@ -0,0 +1,38 @@
+.breadcrumb
+  display: flex
+  flex-wrap: wrap
+  padding: $breadcrumb-padding-y $breadcrumb-padding-x
+  margin-bottom: $breadcrumb-margin-bottom
+  list-style: none
+  background-color: $breadcrumb-bg
+
+  +border-radius($breadcrumb-border-radius)
+
+.breadcrumb-item
+  // The separator between breadcrumbs (by default, a forward-slash: "/")
+  + .breadcrumb-item
+    padding-left: $breadcrumb-item-padding
+
+    &::before
+      display: inline-block
+
+      // Suppress underlining of the separator in modern browsers
+      padding-right: $breadcrumb-item-padding
+      color: $breadcrumb-divider-color
+      content: $breadcrumb-divider
+
+  // IE9-11 hack to properly handle hyperlink underlines for breadcrumbs built
+  // without `<ul>`s. The `::before` pseudo-element generates an element
+  // *within* the .breadcrumb-item and thereby inherits the `text-decoration`.
+  //
+  // To trick IE into suppressing the underline, we give the pseudo-element an
+  // underline and then immediately remove it.
+  + .breadcrumb-item:hover::before
+    text-decoration: underline
+
+  // stylelint-disable-next-line no-duplicate-selectors
+  + .breadcrumb-item:hover::before
+    text-decoration: none
+
+  &.active
+    color: $breadcrumb-active-color