* Added rudimentary command line interface.
* Added documentation on the CLI.
* Added example output.
* Removed _optional wrapper in favour of the built-in get() method.
* Added --version option.
* Removed default for 'attendee'.
* Looping over all vevents now.
* Updated changelog.
There are currently some issues:
* The layout is too narrow
* Everything is on one page
* Sphinx throws several warnings
* The order is random
* Everything is documented