Raise `click.BadParameter` if config contains unknown keys

[sphuber]

Fixes #11

Before, any keys in the configuration file that did not match any parameters of the command would be silently ignored. This could lead to confusion with users if they accidentally mistyped a parameter in the configuration file.

Here, the configuration_callback method is updated to cross-reference the keys in the configuration file with the names of the command's parameters. If any keys are not recognized a click.BadParameter is raised indicating the unrecognized keys.