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

static/assets/bootstrap/sass/_badge.sass

@@ -0,0 +1,43 @@
+// Base class
+//
+// Requires one of the contextual, color modifier classes for `color` and
+// `background-color`.
+
+.badge
+  display: inline-block
+  padding: $badge-padding-y $badge-padding-x
+  font-size: $badge-font-size
+  font-weight: $badge-font-weight
+  line-height: 1
+  text-align: center
+  white-space: nowrap
+  vertical-align: baseline
+
+  +border-radius($badge-border-radius)
+
+  // Empty badges collapse automatically
+  &:empty
+    display: none
+
+// Quick fix for badges in buttons
+.btn .badge
+  position: relative
+  top: -1px
+
+// Pill badges
+//
+// Make them extra rounded with a modifier to replace v3's badges.
+
+.badge-pill
+  padding-right: $badge-pill-padding-x
+  padding-left: $badge-pill-padding-x
+
+  +border-radius($badge-pill-border-radius)
+
+// Colors
+//
+// Contextual variations (linked badges get darker on :hover).
+
+@each $color, $value in $theme-colors
+  .badge-#{$color}
+    +badge-variant($value)