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

static/assets/bootstrap/sass/_functions.sass

@@ -0,0 +1,76 @@
+// Bootstrap functions
+//
+// Utility mixins and functions for evaluating source code across our variables, maps, and mixins.
+
+// Ascending
+// Used to evaluate Sass maps like our grid breakpoints.
+=_assert-ascending($map, $map-name)
+  $prev-key: null
+  $prev-num: null
+
+  @each $key, $num in $map
+    @if $prev-num == null
+      // Do nothing
+    @else if not comparable($prev-num, $num)
+      @warn "Potentially invalid value for #{$map-name}: This map must be in ascending order, but key '#{$key}' has value #{$num} whose unit makes it incomparable to #{$prev-num}, the value of the previous key '#{$prev-key}' !"
+    @else if $prev-num >= $num
+      @warn "Invalid value for #{$map-name}: This map must be in ascending order, but key '#{$key}' has value #{$num} which isn't greater than #{$prev-num}, the value of the previous key '#{$prev-key}' !"
+
+    $prev-key: $key
+    $prev-num: $num
+
+// Starts at zero
+// Another grid mixin that ensures the min-width of the lowest breakpoint starts at 0.
+=_assert-starts-at-zero($map)
+  $values: map-values($map)
+  $first-value: nth($values, 1)
+
+  @if $first-value != 0
+    @warn "First breakpoint in `$grid-breakpoints` must start at 0, but starts at #{$first-value}."
+
+// Replace `$search` with `$replace` in `$string`
+// Used on our SVG icon backgrounds for custom forms.
+//
+// @author Hugo Giraudel
+// @param {String} $string - Initial string
+// @param {String} $search - Substring to replace
+// @param {String} $replace ('') - New value
+// @return {String} - Updated string
+@function str-replace($string, $search, $replace: "")
+  $index: str-index($string, $search)
+
+  @if $index
+    @return str-slice($string, 1, $index - 1) + $replace + str-replace(str-slice($string, $index + str-length($search)), $search, $replace)
+
+  @return $string
+
+// Color contrast
+@function color-yiq($color)
+  $r: red($color)
+  $g: green($color)
+  $b: blue($color)
+
+  $yiq: ($r * 299 + $g * 587 + $b * 114) / 1000
+
+  @if $yiq >= $yiq-contrasted-threshold
+    @return $yiq-text-dark
+  @else
+    @return $yiq-text-light
+
+// Retrieve color Sass maps
+@function color($key: "blue")
+  @return map-get($colors, $key)
+
+@function theme-color($key: "primary")
+  @return map-get($theme-colors, $key)
+
+@function gray($key: "100")
+  @return map-get($grays, $key)
+
+// Request a theme color level
+@function theme-color-level($color-name: "primary", $level: 0)
+  $color: theme-color($color-name)
+  $color-base: if($level > 0, $black, $white)
+  $level: abs($level)
+
+  @return mix($color-base, $color, $level * $theme-color-interval)