Issue #50 quick fix - append templateName to locals.templatePath

Here's a quick fix for [Issue #50](https://github.com/niftylettuce/node-email-templates/issues/50), where `locals.templatePath` is incomplete because it's missing the `templateName` therefore `templateManager.render()` does not know which engine to use. With this fix Nodemailer batch emails are now properly being rendered by the template engine.