Added NTLM authentication
feature #414 Added NTLM authentication (wardpeet)

This PR was merged into the 5.1-dev branch.

Discussion
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Added NTLM authentication

I added ntlm auth and tests. Not sure if the configuration files are right.

I cleaned my fork up and created a new pull request cause this was easier for me than cleanup the other repo. So it's the same as https://github.com/swiftmailer/swiftmailer/pull/388

Commits
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5292393 Added NTLM authentication
bumped version to 5.1.0-DEV
made some modification to previous merge