Merge pull request #26 from Zelakto/patch-1

Adds "mail_from" to the Documentation

Author: tobyzerner

_docs/installation.md

@@ -142,6 +142,7 @@ There's currently no GUI to configure SMTP (see [#258](https://github.com/flarum
 ```
 mail_driver: smtp
 mail_host: ...
+mail_from: ...
 mail_port: ...
 mail_username: ...
 mail_password: ...