3.0.0-beta2

Changes since the latest beta:

Classes have been reorganized in order to simplify PSR-4 loading
youtube-dl and ffmpeg commands are now logged when debug mode is enabled
The Config and LocaleManager classes now use a factory pattern instead of a singleton
404 and 405 error pages now have the same style as the other pages
The new "defaultAudio" option allows converting to audio by default (thanks to @bellington3)
The Heroku build now uses Python 3 (thanks to @telegrambotdev)
The app now supports the container Heroku stack (thanks to @telegrambotdev)
The new "convertSeek" option allows disabling seeking when converting to audio (thanks to @bellington3)
Exceptions are now logged
AllTube can now run correctly behind a reverse proxy with a custom path or port (thanks to @bellington3)