Added more information to date format error

[Sinirlan]

I modified output string of error message to include row, column and value causing date format error so it's easier to find a problem with source file.

Output looks like this: Error: potential invalid date format at row: 1672, column: BW, value: 24568465

I also updated readme and in script description of delimiter parameter to include FS separator from my previous pull request #267