Add --noHeaderLine option for mongoexport please

I noticed that the mongoimport tool has the option --HeaderLine, but the mongoexport has not.

In fact, I want to export a collection as CSV format and use it in hive. But the first line are fields, not data. I have to process the big file just for removing the first line.

I have reviewed the code of mongoexport at github, The master branch still has the problem.

// Write headers
err = exportOutput.WriteHeader()
if err != nil

I think mongoexport need to add an option like mongoimport's --HeaderLine,