Merge upstream (#111)

app/javascript/mastodon/components/column_back_button.js

@@ -19,10 +19,10 @@ export default class ColumnBackButton extends React.PureComponent {
 
   render () {
     return (
-      <div role='button' tabIndex='0' onClick={this.handleClick} className='column-back-button'>
+      <button onClick={this.handleClick} className='column-back-button'>
         <i className='fa fa-fw fa-chevron-left column-back-button__icon' />
         <FormattedMessage id='column_back_button.label' defaultMessage='Back' />
-      </div>
+      </button>
     );
   }