Fixed a bug with the Password field in the Configuration Dialog
on Windows. Added a check in the Send function that made sure
it could open the attachments before trying to send the email.
(It used to only check when it was actually sending the email,
meaning that if the attachment couldn't be read, it would send
the email without the attachment. The check is now just earlier
in the process.) Fixed a problem on Windows where certain ISPs
would include an @ symbol when setting the Host Name of the
computer, causing mail servers to give an error when SMTPit was
trying to identify itself. Fixed a problem on OS X where the status dialog wasn't updating properly.
