learn.jquery.com: Change permalinks on the footer of articles

Fixes jquery/learn.jquery.com#647
Closes gh-358

Author: sigorilla

themes/learn.jquery.com/content-page.php

@@ -20,15 +20,15 @@
 		<div class="bottom-links row">
 			<?php if (isset($next_prev_arr['prev'])): ?>
 				<div class="prev six columns">
-					<a href="<?php echo $next_prev_arr['prev']->guid; ?>">
+					<a href="<?php echo get_page_link( $next_prev_arr['prev']->ID ); ?>">
 					<i class="icon-chevron-left"></i>
 					<?php echo $next_prev_arr['prev']->post_title; ?>
 					</a>
 				</div>
 			<?php endif; ?>
 			<?php if (isset($next_prev_arr['next'])): ?>
 				<div class="next six columns">
-					<a href="<?php echo $next_prev_arr['next']->guid; ?>">
+					<a href="<?php echo get_page_link( $next_prev_arr['next']->ID ); ?>">
 					<?php echo $next_prev_arr['next']->post_title; ?>
 					<i class="icon-chevron-right"></i>
 					</a>