PHP >=5.5 deprecates the /e modifier for preg_replace

PHP >=5.5 deprecates the /e modifier for preg_replace, preg_replace_callback should be used instead

Hi,

I recently started working at LevelSet Solutions where I understand you started developing pomander. Today I ran into an issue with PHP 5.5 and preg_replace using the /e modifier. I have error_reporting set to E_ALL in php.ini as is recommended for a development environment, which caused 'pom setup' to fail. I tracked it down to pomander-wordpress/lib/taks.php:82, so I wrote an equivalent preg_replace_callback to replace the preg_replace using the /e modifier and then pom setup succeeded.

Anyway, just wanted to contribute that change.