added checkbox to the TabulatrData DSL
Added `id` of record as `data-id` of table row in static table if
id is available.
Added `row` to the TabulatrData DSL to provide HTML attributes for the
  table_row of each record.

Example:
  ```
  row do |record, row_config|
    if record.super_important?
      row_config[:class] = 'important';
    end
    row_config[:data] = {
      href: edit_user_path(record.id),
      vip: record.super_important?
    }
  end
  ```
update bootstrap-sass gem
better error message
fix stupid spec
raise error when requested attribute is not defined in TabulatrData class
improved js
refactored apply_condition method
make js more object oriented