Render an individual tiddler as a specified ContentType, defaulting to `text/html` and save it to the specified filename. Optionally a template can be specified, in which case the template tiddler is rendered with the "currentTiddler" variable set to the tiddler that is being rendered (the first parameter value).
By default, the filename is resolved relative to the `output` subdirectory of the edition directory. The `--output` command can be used to direct output to a different directory.