Default driver is not what the README claims

[dimbleby]

README says:

• driver

String. ODBC Driver to use ("ODBC Driver 17 for SQL Server", "SQL Server Native Client 11.0", "FreeTDS" etc). Default is "ODBC Driver 17 for SQL Server".

code says:

driver = options.get('driver', 'ODBC Driver 13 for SQL Server')

(I found this because 17 is the value that one actually needs in an Azure App Service. But since the README told me that was the default, I left it alone; and then it didn't work.)

[absci]

Thanks for the report, I'll change the default value accordingly to match the README file.