Reconsider __str__ behavior

[Aran-Fey]

Currently, __str__ automatically finds a suitable unit. Some people have said they don't like this behavior, and would rather see it printed "as-is" (like __repr__ does).

Perhaps it would be wise to implement __format__, allowing users to choose a unit or use * for auto-conversion. Examples:

f'{download_speed}'  # use the current unit
f'{download_speed:*}'  # automatically find the most suitable unit
f'{download_speed:*/s}'  # find a suitable unit given the constraint `/s`