Change the "short example" to use the GMailSMTP class

[cartr]

Instead of using "smtp.googlemail.com" directly, the "Short Example" from the documentation should use the preconfigured GMailSMTP class. This makes the code a little easier to follow, as server settings don't need to be included.

[tomekwojcik]

Hi,
I decided to add your code along the current information so the docs showcase both options of sending an envelope.

Thanks for your contribution and interest in the project.

PS. Would you mind if I added you to AUTHORS.rst file?

[cartr]

Sure, you can add me to the AUTHORS.rst file.

[tomekwojcik]

Great. Thanks!