Upgrade arrow to > 0.12.1

[fluffy-critter]

This is a placeholder to remind myself to check for Arrow upgrades; 0.12.1 doesn't support tzinfo specification for strings, but the next version will.

[fluffy-critter]

Of course now that dates sort and paginate based on the naive datetime, this is less important as it only affects post scheduling.

[fluffy-critter]

Reopening, since I still want to have a thing to check for.

[systemcatch]

@fluffy-critter arrow 0.13.0 has finally been released if you want to check it out.

[fluffy-critter]

Ah, thanks! I had actually noticed it was on 0.13.0 now but I forgot that's the version I was waiting for. :)