Responsive images in Wordpress posts

functions.php

// Remove image width/height, so everything can work responsively in posts
function strip_size($html, $id) {
	$html = preg_replace('/\<(.*?)(width="(.*?)")(.*?)(height="(.*?)")(.*?)\>/i', '<$1$4$7>',$html);
	return $html;
}

add_filter('get_image_tag', 'strip_size', 10, 2);

function remove_thumbnail_dimensions( $html ) {
	$html = preg_replace( '/(width|height)=\"\d*\"\s/', "", $html );
	return $html;
}

add_filter( 'post_thumbnail_html', 'remove_thumbnail_dimensions', 10 );
add_filter( 'image_send_to_editor', 'remove_thumbnail_dimensions', 10 );
add_filter( 'wp_get_attachment_image_attributes', 'remove_thumbnail_dimensions', 10 );