298-change "sticky-footer" mixin to target <footer> selector (#299)

remove parent <footer> element from the Global Footer component and include it instead in kss/builder/decanter/index.twig.  The Global Footer component is now a <section> to be included in a a sites <footer> region.  Also added some comments to global-footer.twig which mirror what are in the brand-bar component.

core/scss/components/brand-bar/_brand-bar.scss

@@ -21,9 +21,6 @@
 
 .su-brand-bar__container {
   @include centered-column;
-  @include grid-media-only('xs') {
-    @include padding(null 20px);
-  }
 }
 
 .su-brand-bar__logo {

core/scss/components/global-footer/_global-footer.scss

@@ -11,7 +11,7 @@
 //
 
 // Global styles for the global footer.
-.global-footer {
+.su-global-footer {
   @include modular-spacing(1, 'padding-top');
   @include modular-spacing(1, 'padding-bottom');
   background-color: $color-cardinal-red;
@@ -28,15 +28,15 @@
   }
 
   // Grid settings for footer container.
-  .global-footer__container {
+  .su-global-footer__container {
     @include centered-column;
     @include grid-media('md') {
       display: flex;
     }
   }
 
   // The Logo.
-  .global-footer__brand {
+  .su-global-footer__brand {
     @include padding(0.5rem null null);
     @include modular-spacing(-2, 'margin-bottom');
     text-align: center;
@@ -52,7 +52,7 @@
     }
   }
 
-  .global-footer__content {
+  .su-global-footer__content {
     @include grid-media-only('sm') {
       text-align: center;
     }
@@ -86,7 +86,7 @@
     }
   }
 
-  .global-footer__menu {
+  .su-global-footer__menu {
     @include margin(0 0 1rem);
     @include padding(0);
     list-style-type: none;
@@ -117,7 +117,7 @@
     }
   }
 
-  .global-footer__menu--global {
+  .su-global-footer__menu--global {
     font-size: 1.5rem;
 
     @include grid-media-only('xs') {
@@ -133,7 +133,7 @@
     }
   }
 
-  .global-footer__menu--policy {
+  .su-global-footer__menu--policy {
     font-size: 1.5rem;
     font-weight: 300;
 
@@ -155,7 +155,7 @@
     }
   }
 
-  .global-footer__copyright {
+  .su-global-footer__copyright {
     font-size: 1.4rem;
     font-weight: 300;
     text-align: center;

core/scss/utilities/mixins/layout/_sticky-footer.scss

@@ -1,8 +1,5 @@
 @charset 'UTF-8';
 
-// This file is here until https://github.com/SU-SWS/decanter/pull/261 gets
-// merged and pulled in to this project.
-
 //
 // @sticky-footer
 //
@@ -15,12 +12,12 @@
 // at the bottom of the page when the content is shorter than the window, but allow
 // the content to push the footer below the viewport when the page is long.
 //
-// $selector - the CSS selector used to target the footer; default '> footer'
+// $selector - the CSS selector used to target the footer; default '> .site-footer'
 //
 // Style guide: Mixins.Layout.Sticky Footer
 //
 
-@mixin sticky-footer($selector: '> .global-footer') {
+@mixin sticky-footer($selector: '> .site-footer') {
   @include padding(0);
   @include margin(0);