Update AbstractSmtpTransport.php

Swift_TransportException should include the status code from the smtp backend.
merged branch returngreat/master (PR #305)

This PR was merged into the master branch.

Commits
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7636029 Update AbstractSmtpTransport.php

Discussion
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AbstractSmtpTransport should include the status code in the exception

Swift_TransportException should include the status code from the smtp backend.