Fix malformed address

Hello

All mail sent by Gogs is automatacaly flaged as spam by my own MTA (based on exim).
It's because the header doesn't follow the Exim guidelines.

Only the "" (and the space after them) is missing around the From attribute.
Please see this link for more informations : https://github.com/Exim/exim/wiki/Q0087

Can you check if i'm doing right ? I'm not familiar with Go language ^^"