Add column/data zipping functionality

[ollietulloch]

This PR adds column zipping functionality to the mapper, where 2 (or more) columns can have their string values split by a given split_char and then be zipped together in a prescribed order.

E.g. given this csv data

"title","value"
"species,colour,legs","dog,brown,4"

and this data:

    - column: title
      mappings:
      - field: zipped_field
        zip_order: 1
        split_char: ","
    - column: value
      mappings:
      - field: zipped_field
        zip_order: 2

This mapped_line would be produced:

{ "zipped_field"=>[["species", "dog"], ["colour", "brown"], ["legs", "4"]],
   :rawtext=>{"title"=>"species,colour,legs", "value"=>"dog,brown,4"}}

[bshand]

This all looks good to me. I've identified one minor typo.

I don't know whether you want to add any sort of validations (or error handling in the mapping code), to deal with incomplete zip_order entries or the absence of a split_char.

[ollietulloch]

This all looks good to me. I've identified one minor typo.

I don't know whether you want to add any sort of validations (or error handling in the mapping code), to deal with incomplete zip_order entries or the absence of a split_char.

Yep, I thought about this a bit. I think I may just update the code to check for :zipped_values and :split_char before attempting the splitting and zipping e.g.

elsif field_data[:zipped_values].present? && field_data[:split_char].present?

[ollietulloch]

This all looks good to me. I've identified one minor typo.
I don't know whether you want to add any sort of validations (or error handling in the mapping code), to deal with incomplete zip_order entries or the absence of a split_char.

Yep, I thought about this a bit. I think I may just update the code to check for :zipped_values and :split_char before attempting the splitting and zipping e.g.

elsif field_data[:zipped_values].present? && field_data[:split_char].present?

I've added 58a7b92 which ensures there is enough field config present before attempting to zip.

[bshand]

This all looks good.