Fixing returns in PHPdoc

My IntelliJ (IDE) complains in the method handler() because the PHPdoc for Kohana_Exception::_handler() told it that a boolean was returned. The "boolean" was then used as an Response object. Since a Response was the actual returned value, I fixed the PHPdoc.
Merge pull request #373 from HNygard/patch-1

Fixing returns in PHPdoc

Refs #4762