Revert "Merge branch 'luciferous-master' into dev"

This reverts commit 9202a37cf517a24b17fb554adbab5c6bfbb227bd, reversing
changes made to 54b5800d420da0dea307fa79518f181f3dbe5554.

Using `is_callable` is problematic as the `__call` magic method interferes with
context all over the place. See http://hile.mn/buBS11 and http://hile.mn/9vy1S6

Mustache.php

@@ -604,7 +604,7 @@ class Mustache {
 	protected function _findVariableInContext($tag_name, $context) {
 		foreach ($context as $view) {
 			if (is_object($view)) {
-				if (is_callable(array($view, $tag_name))) {
+				if (method_exists($view, $tag_name)) {
 					return $view->$tag_name();
 				} else if (isset($view->$tag_name)) {
 					return $view->$tag_name;