CSVRecord mutability

I recently pushed a change(pull request 20) to get the line ending from the parser.

Now I want to push another change which I feel will also be useful for the community. I want to add a CSVRecordMutable class which had a constructor which accepts a CSVRecord object. So when we have a CSVRecordMutable object from it then we can edit individual columns using it.

I would be using this to write back my edited CSV file. My use case is to read a csv, mangle some columns, write back a new csv.

I could have directly raised a pull request but I just wanted to float the idea before and see the reaction.