add support for SMTP server authentication using NTLM

[shadiakiki1986]

• Largely copied from https://www.pythondiary.com/tutorials/django-ntlm-smtp-auth.html
• includes the case of decode('utf-8') as documented in NTLM auth value not decoded properly. Value contains 'b//' #23 and solved by arijeetmkh@5f75780
• also included an example script to demonstrate sending emails through such server

[coveralls]

Coverage decreased (-2.3%) to 91.787% when pulling e505210 on shadiakiki1986:feature_smtp into e660efe on trustrachel:master.

[shadiakiki1986]

FYI for any future-comers here, until this PR advances, I published the pypi package shadiakiki1986-python-ntlm3 containing this patch