Fixed setSheet in wrong interface

Update README.md

Added testes for "Fixed writeCell() after writeRow() in same row inde…

…x throwing "Writing row backward" exception"

Updated auto detect logic

Merge pull request #1 from atlas-wong/master

Enhanced performance using phpexcel to read xlsx file

Cleanup

Fixed PHPExcelWriter stream mode

Update README.md

Pulled up input_format, output_format, added method $excel->getOutput…

…Extension()

Updated README.md