Add the ability to delete multiple columns

[wowinter13]

When I was working with some statistics using Ruby/csv, I discovered that the mechanism for deleting columns is very peculiar in Ruby and we can't easily just delete more than 1 column.
We can do it like this (DRY):

csv_table.delete("PassengerId")
csv_table.delete("Survived")
csv_table.delete("Name")
csv_table.to_csv

Or like this (will destroy csv structure -> Array of Arrays):

datus = CSV.readlines('titanic.csv', headers:true).map{|row| row.values_at('PassengerId','SibSp') }

And finally the best working way for me:

to_del = ["Name", "Ticket"]
csv_table = datus.by_col!.delete_if { |name, values| !to_del.include? name}

But I think it should work easily like this:

to_del = ["Name", "Ticket"]
data.delete(to_del)

So I rewrote method a little and added this functionality. If you have any ideas: create another delete_columns method or maybe better ways to fast delete columns, I will be glad to hear it:)

[kou]

*indexes_or_headeres is better than accepting an Array argument.

[kou]

This method should return the deleted objects.

indexes_or_headers.map do |index_or_header|
  delete(index_or_header)
end

[wowinter13]

@kou Thanks for review and I changed checked methods. Can you view current version please?

[kou]

Thanks.
I've merged and reverted zero argument (raising ArgumentError) and one argument (returning without wrapping by an Array) case behavior for backward compatibility.