Correct namespaces + Hack to load the temporary implementation class.

Hi.

Here two little corrections : 
* correction of namespaces : \michelf to \Michelf
* in SmartyPantsTypographer.php, add a hack to load the temporary implementation class (on the model of MarkdownExtra).

These corrections are necessary to use your library in PHP5 without modification.

Regards.
Mathieu Poisbeau