Add support for Array columns.

[mikeeus]

I would really like to see this feature because I use arrays quite often. I plan to work on this issue myself when I have the time, possibly next week.

I also use JSONB columns, but it's not a priority for me at the moment, and I'm not sure how I would implement this. But I'll think about it once this issue is resolved.

[paulcsmith]

I love this idea, but I'd like to add better support in LuckyRecord before adding it to migrator. I think for now doing it with execute is ok.