Fix datetime

[isaacmg]

We need to remove the requirement to have a date time column. Instead have the sort_column param fit this role https://github.com/AIStream-Peelout/flow-forecast/blob/2c1570d6f8615c6e28c62169e87190fec1d77248/flood_forecast/preprocessing/pytorch_loaders.py#L158

[isaacmg]

This issue should be pretty easy for first timers to fix

[isaacmg]

Ugh this is becoming a pain. It should be fixed before release 1.0