Fix variable reference and incorrect parameter
Updated Error class to be raise-able and output relevant info
Updated file_name to include the fileName from salesforce
Added more user feedback
Added progress meter to download
Multi-file download, email, and retry logic. More...

Updated main loop to account for multiple files in the index list
Moved email logic out of download method
Updated download failure to raise an error, and the email method to receive it
Added retry logic to download attempts