Add output log file for `cues`

Currently `cues` only prints out the results of the inspection on the terminal, Mark W mentioned it would be nice to have the possibility to save this information.
- Add a `-o` option to the parser.
- Save a copy of the printed out `cues` output in a log file.

In the first instance, it's probably just enough to open a file in a context message and write the printed out lines to it.
But, this might also be a good starting point to look into adding a bit of logging to the code (see #30 ).