Saving over a metadata can cause confusing errors when the newer run has fewer states

[BaxterEaves]

If you do something like

$ lace run --csv small.csv -s 8 -n 1000 metadata.lace
$ lace run --csv big.csv -s 4 -n 1000 metadata.lace

where you save to a metadata directory with a large number of states lace will happily load metadata.lace but when you try to do certain things you'll get strange errors (usually index errors).

FIX

Future versions on the metadata could have a hash for the codebook in the state metadata. This would be a breaking change, so maybe just checking the number of rows, number of columns and feature types in each state during load would suffice for now.