Readme update - added email attribute and example command

[versedi]

I've forgot to update readme when creating last commit and pull request.

Readme updated with --email="1" and example command in use.

[kalenjordan]

You know what actually can we change the command line option from --email to --send-email? Having email as a parameter feels like it is going to force a value for the customer email in the order that's created.

[versedi]

I was giving it a thought but decided to keep it short - it's indeed not so obvious so I think it'd be better.

[kalenjordan]

Thanks!