xlsx_buffer v1.0.2

This is a copy of xlsx module. I made few changes in this module to accept buffer. This module is being used in xlsx_buffer_json. Please check this url https://github.com/motomohg/workspace.git on how to use xlsx_buffer_json.In that example app, you can upload excel sheet and parse it into buffer without uploading in any temp directory. Then pass that buffer xlsx_buffer_json to get list of js objects which you can use to update DB tables