Replace extras.php with template-functions.php

fixes #1064

inc/template-functions.php

@@ -0,0 +1,27 @@
+<?php
+/**
+ * Additional features to allow styling of the templates
+ *
+ * @package _s
+ */
+
+/**
+ * Adds custom classes to the array of body classes.
+ *
+ * @param array $classes Classes for the body element.
+ * @return array
+ */
+function _s_body_classes( $classes ) {
+	// Adds a class of group-blog to blogs with more than 1 published author.
+	if ( is_multi_author() ) {
+		$classes[] = 'group-blog';
+	}
+
+	// Adds a class of hfeed to non-singular pages.
+	if ( ! is_singular() ) {
+		$classes[] = 'hfeed';
+	}
+
+	return $classes;
+}
+add_filter( 'body_class', '_s_body_classes' );