Use the name var_name consistently
Update TODO list
Add missing parenthesis
Add initial support for optional parameters
Print the command list as well
Fix typo
Add support for testing missing required parameters

Change the spec so that a key and value setting is separated by a
equals sign instead of space. This allows to have settings that
don't have a correspondent value associated (e.g. --help).

Also change example.py to have a concept of subcommands.
Fix bug caused by optional parameters

Also, add support for tests with *valid* numeric ranges.
Support tests which don't give any value for some setting
Pass the settings dictionary instead of error_string

This will make it to add more settings in the future.
Rename variable for clarity
Update TODO
Refactor a bit the code
Separate arguments and parameters by a space

Separate arguments and parameters by a space instead of an equals
sign, as both short and GNU long options can be specified this
way.
Fix a bug: search for the right value

We need to look up for the option, not the option's value in
the optional_params list.
Protect regexes by start and end anchor
Improve example.py and its associated spec
Update TODO
Add documentation
Remove old debugging print