argument parsing: Fixed code path for parsing --colour-pony accessing an undefined variable.
list.py: Removed unused import.
ponysay.py: Added missing import.

The module leaked from some other module via a * import.
ponysay.py: Converted methods which are never called on an instances to class methods.
list.py: Moved static functions to module level.
list.py: Removed unnecessary calls to gettermsize().
list.py: Extracted duplicate code for listing files in a directory into a utility function.
list.py: Renamed list module to lists to avoid conflict with builtin.
setup.py: Automatically collect a list of source files to distribute.

This will help with refactoring, where source files may be added and/or moved.
lists.py: Rewritten list formatting code.

- Split up into functions for distributing the items into columns and actual formatting and printing of the columns.
- Fixes printing when console is narrower than the longest name.