Django-sitemessage

-------------------
* Fixed 'proxies' parameter passing.
* Fixed possible dispatches jamming in 'Processing' status.

-------------------
! Dropped Python 2 support.
+ Messengers using 'requests' ('vk', 'fb', 'telegram') now support proxies.

-------------------
! Dropped QA for Django 1.7.
! Dropped QA for Python 2.
+ Add Django 3.0, removed 1.8 compatibility. Effectively deprecates Py2 support.

------
! Dropped QA for Python 3.4.
* No functional changes. Celebrating 1.0.0.

-------
* Fixed 'NotSupportedError' on some old DBMSs.

-------
! Renamed bogus 'SITEMESSAGE_DEFAULT_SHORTCUT_EMAIL_MESSAGES_TYPE' setting into 'SITEMESSAGE_SHORTCUT_EMAIL_MESSENGER_TYPE'.
+ Added 'sitemessage_check_undelivered' command and 'check_undelivered()' function (closes 7).
+ Added 'SITEMESSAGE_SHORTCUT_EMAIL_MESSAGE_TYPE' to replace 'SITEMESSAGE_DEFAULT_SHORTCUT_EMAIL_MESSAGES_TYPE'.
+ Added dispaches delivery retry in admin (closes 8).
+ SMTPMessenger. Added SSL support (closes 10).
+ SMTPMessenger. Added timeout support (closes 9).