Breaking: Split::IntoMultipleColumns now requires max_segments param

Kiba processes data one row at a time. No single row knows about the qualities of other rows.

Also, it is expected that rows will all have the same fields.

Therefore, it was a problem if one row's value was going to be split into 5 columns, while another row's would be split into 2 columns.

Now you have to tell the Split::IntoMultipleColumns transform how many columns to create. These will be created for all rows and filled in with nil (blank in output spreadsheet) if the split value doesn't fill them all in for a given row.

This is a breaking change To fix any errors, provide a value for the max_segments parameter when calling this transformation.