v0.1.0

First version of the library.

The features available are:
Converting a list of objects into an Excel file
Converting an Excel file into a list of objects
Converting an Excel file to CSV
Converting a CSV file to Excel.
Opening, creating and closing a Workbook
Opening, creating and closing a Sheet. Various operations with the sheet.
Methods to check if the extension is valid, count all rows (excluding or not empty ones) in one or more Sheets