BugFix: Add directory separator to end of searchpath elements.

Fix failing unittests (could not find template exceptions):

    $h2o = h2o('emails/base.html', array(
                'searchpath' => dirname(__FILE__).DS.'templates'
            ));

Did not find the template because it searched for `templatesemails/base.html` instead of for
`templates/emails/base.html`