v2.0.0

Breaking Changes

• Adds Mailer.deliver_now! and deliver_later! (#571)
• Extract Bamboo.Phoenix (#581)
• Remove deprecated code (#580)

Please see the upgrade guide.

Additions/Improvements

• Update SendGrid Adapter to return ok/error tuple (#572)
• Update Mailgun.deliver to return ok/error tuples (#573)
• Update Mandrill to return ok/error tuples (#574)
• Adds upgrade guide to Bamboo 2.0 (#582)