add english-lang and fix cronjob, fixes #1

MensaPlugin.class.php

README.md

assets/images/alkohol.png

assets/images/bio.gif

assets/images/gefluegel.png

assets/images/knoblauch.gif

assets/images/rindfleisch.gif

assets/images/schweinefleisch.gif

assets/images/vegan.png

assets/images/vegetarisch.png

assets/mensa-widget.css

assets/mensa-widget.js

assets/mensa-widget.less

classes/MensaCronjob.class.php

classes/MensaHelper.class.php

migrations/01_add_cronjob.php

migrations/02_add_config.php

migrations/03_add_config_location.php

plugin.manifest

templates/exception.php