Moving aria-label to div.column (#1769)

* Use landmark regions on columns

Closes mastodon#1720

* Moving aria-label to div.column

app/assets/javascripts/components/features/ui/components/column.jsx

@@ -64,7 +64,7 @@ const Column = React.createClass({
     }
 
     return (
-      <div role='section' className='column' onWheel={this.handleWheel}>
+      <div role='section' aria-label={heading} className='column' onWheel={this.handleWheel}>
         {header}
         {children}
       </div>