Gist oembed support.

gistfile1.txt

function bhww_embed_handler_gist( $matches, $attr, $url, $rawattr ) {
        $embed = sprintf(
	      '<script src="https://gist.github.com/%1$s.js%2$s"></script>',
	      esc_attr($matches[1]),
	      esc_attr($matches[2])
        );

        return apply_filters( 'embed_gist', $embed, $matches, $attr, $url, $rawattr );
}
wp_embed_register_handler( 'gist', '/https?:\/\/gist\.github\.com\/([a-z0-9]+)(\?file=.*)?/i', 'bhww_embed_handler_gist' );