Fix sticky search bar disappearing when cart is open.

So I think the issue is that all the HTML is wrapped on an
`off-canvas-wrap` class that is used for doing the sidebar car open over
main content. The problem is that when this car sidebar is open body of
HTML overflow is changed to `overflow: hidden` and search bar use CSS
`position: sticky;` which doesn't work  when its parent has overflow
hidden. The issue was that `off-canvas-wrap` had an `overflow: inherit`
which means when body is set to overflow hidden this div inherits it and
break search bar position sticky when cart sidebar is opened. The
solution is to use `position: initial` which means use what a div has as
default value for `overflow` which I think it's `visible`. This class is
overriding the same class that comes from Foundation Framework that set
this div to be `overflow: hidden`. The override was added when [we added
search sticky](ff69389bb0)

More info about the problem with [position:sticky and its parent having
overflow hidden](https://css-tricks.com/dealing-with-overflow-and-position-sticky/) also info about [position initial vs inherit](https://stackoverflow.com/a/29661356)

app/assets/stylesheets/darkswarm/menu.scss

@@ -212,7 +212,7 @@ nav.top-bar {
 }
 
 .off-canvas-wrap {
-  overflow: inherit;
+  overflow: initial;
 }
 
 .off-canvas-list li.language-switcher ul li {

app/views/layouts/darkswarm.html.haml

@@ -18,14 +18,14 @@
     = stylesheet_link_tag "darkswarm/all"
     = csrf_meta_tags
 
-  %body{class: body_classes, "body-scroll" => true , ng: {app: "Darkswarm"}}
+  %body{ class: body_classes, "body-scroll" => true , ng: { app: 'Darkswarm' }}
     / [if lte IE 8]
       = render partial: "shared/ie_warning"
       = javascript_include_tag "iehack"
 
     = render "layouts/shopfront_script" if @shopfront_layout
 
-    .off-canvas-wrap{offcanvas: true}
+    .off-canvas-wrap{ offcanvas: true }
       .fixed.off-canvas-fixed
         = render "shared/menu/menu" unless @hide_menu
         = yield :page_alert