wrap long text to 72 chars

wrap.rb

def wrap(text)
  result = []
  fenced = false
  text.split(/\r?\n/).each do |line|
    if line.start_with?("```")
      fenced = !fenced
    end
    if fenced || line.size <= 72
      result << line
    else
      buf = ""
      line.split.each do |word|
        if (buf.size + word.size) > 71 # 72 with space
          result << buf
          buf = word
        else
          buf << " " unless buf.empty?
          buf << word
        end
      end
      result << buf unless buf.empty?
    end
  end
  result.join("\n")
end