Replaced preg_replace() with preg_replace_callback() in Hull/Connection.php

This due to [preg_replace()](http://www.php.net/manual/en/function.preg-replace.php) with the /e option being [deprecated](http://php.net/manual/en/migration55.deprecated.php) in php 5.5.0 & now throwing an exception.
The fix is replacing with [preg_replace_callback()](http://www.php.net/manual/en/function.preg-replace-callback.php)

**Note**
- Change creates compatibility with php 5.5.x
- Change breaks compatibility with php 4 < 4.0.5