Set default csv.enclosure config to a "

When writing a CSV file, if the data contains a comma, or a line-break, it can cause different CSV readers to think a new row has been started.

This is why the default `enclosure` setting for [fputscsv](http://www.php.net//manual/en/function.fputcsv.php) is a `"`

I experienced issues with broken CSV files when I moved from using [fputscsv](http://www.php.net//manual/en/function.fputcsv.php) to using this package, until I realised I could set the enclosure in my config, and that fixed the problem.

I have set `"` as the default enclosure within your code and your config.