require_once is redundant and expensive

Great module! I began writing a similar one before I found this one.

One thought:

Using require_once() in the autoload_class() function is redundant. autoload_class() is only called when php can't find a class definition. If the file containing a class was already included, the class defenition would already be loaded and autoload_class() would not be called. Also, many articles on php performance and optimization recommend not using require_once and include_once wherever possible because they are much more expensive operations.