replace '\\"' with '""' for correct escaping of quotes.

[Obeyed]

According to the csv standard, correct escaping of quotation marks is a quotation mark. We noticed an open issue for this problem, and we decided to create a pull request with a fix. As mentioned in the issue (https://github.com/matteofigus/nice-json2csv/issues/8), the fix is simply adding an extra replace to correctly add the quotation mark after the stringify function. :)