* Remove Python 2 specific code
* Require imports to have a proper isort-supported order
* Only test/lint on Python 3
* Bump most dependencies to latest supported version
2.3.0 / 2020-02-17
==================
**General**
* During setup, admins can register their email address with the CTFd LLC newsletter for news and updates
* Fix editting hints from the admin panel
* Allow admins to insert HTML code directly into the header and footer (end of body tag) of pages. This replaces and supercedes the custom CSS feature.
* The `views.custom_css` route has been removed.
* Admins can now customize the content of outgoing emails and inject certain variables into email content.
* The `manage.py` script can now manipulate the CTFd Configs table via the `get_config` and `set_config` commands. (e.g. `python manage.py get_config ctf_theme` and `python manage.py set_config ctf_theme core`)
**Themes**
* Themes should now reference the `theme_header` and `theme_footer` configs instead of the `views.custom_css` endpoint to allow for user customizations. See the `base.html` file of the core theme.
**Plugins**
* Make `ezq` functions available to `CTFd.js` under `CTFd.ui.ezq`
**Miscellaneous**
* Python imports sorted with `isort` and import order enforced
* Black formatter running on a majority of Python code
* Format Javascript and CSS files with `prettier`: `prettier --write 'CTFd/themes/**/*'`
* Format Python with `black`: `black CTFd` & `black tests`
* Travis now uses xenial instead of trusty.
