* Flesh out SendinBlue docs, add a readme mention
* Stop trying to list all the supported ESPs in the project short
description and similar headlines -- it was becoming unwieldy.
* Support `pip install django-anymail[sendinblue]`
and use it in Travis tests (for consistency; SendinBlue
doesn't require any extra packages)
New EmailMessage attribute `envelope_sender` controls ESP's sender,
sending domain, or return path where supported:
* Mailgun: overrides SENDER_DOMAIN on individual message
(domain portion only)
* Mailjet: becomes `Sender` API param
* Mandrill: becomes `return_path_domain` API param
(domain portion only)
* SparkPost: becomes `return_path` API param
* Other ESPs: not believed to be supported
Also support undocumented Django SMTP backend behavior, where envelope
sender is given by `message.from_email` when
`message.extra_headers["From"]` is set. Fixes#91.
Add support for sending transactional email through SendinBlue. (Thanks to @RignonNoel.)
Partially implements #84. (Tracking webhooks will be a separate PR. SendinBlue doesn't support inbound handling.)
