config file

Use config file to store

- display options such as frame position/size
- fallback values for command line parameters

Config files can be accessed with [ConfigParser](http://docs.python.org/2.7/library/configparser.html).

Note, that the second issue probably is easier to accomplish using [argparse](http://docs.python.org/2.7/library/argparse.html) rather than [docopt](http://docopt.org/). It might be possible with *docopt* to use a [`defaultdict`](http://docs.python.org/2.7/library/collections.html#collections.defaultdict) with one section of the config file as the fallback.