Extract printing behaviour into a report or summary method with a default implementation

[drmason13]

Currently this is done inline in the run method.

// TODO: extract printing behaviour into a report or summary method with a default implementation
println!(
    "Day {0}, Part 1\n\
    {1}\n\n\
    Day {0}, Part 1\n\
    {2}",
    Day, part1_output, part2_output
);

I can foresee plenty of reasons to want to customise this and I'd like to enable that more easily.

Separating into two methods means the user can do that without having to re-implement the running of part1 and part2 which is a bit more involved..

[drmason13]

Oh I should fix that it prints "Part 1" both times, yikes!