v1.0.1

• Added user's input validation message
• Added root.update_idletasks() to update the loop tasks, rather than displaying "Not responding"

v1.0.0

• Convert Excel files (xlsx, xlsb, xls) to csv or txt files
• Simple and friendly UI
• Can skip rows (i.e. choose header index)
• Can choose sheet index to convert rather than the active sheet or the 1^st sheet