Refactor the css layout to use grid and flex

Remove #primary

Remove #primary, take 2

Change primary layout module to CSS grid.

Remove ::before / ::after based clearfixes. When using flex and grid, pseudo-elements are considered flex/grid elements and cause unexpected behavior. Clearfix is a tool to resolve clearing when using float-based layouts. Modern flex/grid-based layouts do not need them.

Main menu: Use flex as layout module.

Main menu cleanup.

Comments, Posts, and Post Navigation: Use flex for layout. Automatic RTL.

Remove errant test data.

- Fixed skip to content link to point to main content (#primary).
- Changed ID for <main> to #primary to preserve original separation between main and sidebar (#secondary).
- Removed superfluous ID reference to #secondary in CSS.
- Cleaned up whitespace triggering Travis errors.

Fix wpcs issues

Cleaning the rebase

Compile CSS

Remove primary div from WooCommerce too

grid-template-columns property doesn't support negative values

index.php

@@ -15,8 +15,7 @@
 get_header();
 ?>
 
-	<div id="primary" class="content-area">
-		<main id="main" class="site-main">
+	<main id="primary" class="site-main">
 
 		<?php
 		if ( have_posts() ) :
@@ -51,8 +50,7 @@ get_header();
 		endif;
 		?>
 
-		</main><!-- #main -->
-	</div><!-- #primary -->
+	</main><!-- #main -->
 
 <?php
 get_sidebar();