Add keyword attributes for table columns

[bradgessler]

The table column should accept any HTML attributes in the table.column method to support adding inline HTML attributes to the th tag in the table.

Table items: Interviewer.all do |table|
  table.column("Interviewer") { show(_1, :name, style: "white-space: nowrap;") }
  InterviewTime.all.each do |time|
    table.column(time.name, style: "white-space: nowrap;") { _1.interviews.build(interview_time: time)
      input(type: :checkbox, checked: [true,false].sample)
     }
  end
end