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

static/assets/bootstrap/sass/_grid.sass

@@ -0,0 +1,43 @@
+// Container widths
+//
+// Set the container width, and override it for fixed navbars in media queries.
+
+@if $enable-grid-classes
+  .container
+    +make-container
+    +make-container-max-widths
+
+// Fluid container
+//
+// Utilizes the mixin meant for fixed width containers, but with 100% width for
+// fluid, full width layouts.
+
+@if $enable-grid-classes
+  .container-fluid
+    +make-container
+
+// Row
+//
+// Rows contain and clear the floats of your columns.
+
+@if $enable-grid-classes
+  .row
+    +make-row
+
+  // Remove the negative margin from default .row, then the horizontal padding
+  // from all immediate children columns (to prevent runaway style inheritance).
+  .no-gutters
+    margin-right: 0
+    margin-left: 0
+
+    > .col,
+    > [class*="col-"]
+      padding-right: 0
+      padding-left: 0
+
+// Columns
+//
+// Common styles for small and large grid columns
+
+@if $enable-grid-classes
+  +make-grid-columns