This is a minor bump of Marrow Mailer addressing the following:

• Somewhat modernized testing harness.
• #61 Corrections for SES issues.
• #64 Documentation updates. (Also: #68)
• #67 Python 3 corrections.
• #69 Better handling of attachment filename encoding.

This release introduces support for additional transports:

• Mailgun
• SendGrid
• Postmark