v2.8.0

@davrux:

• Allows to use a helo other than 'localhost'.

@norguhtar

• Fix add header to correct get from headers.
• RFC1870 fix (send size if extension is supported)

@alex1989hu

• Add golangci-lint action

@yene

• Changed Encryption type to be public so the value can be passed around

@vjeantet

• New public function to get recipients of email GetRecipients
• New function to send a RFC822 formatted message SendMessage