parse out protected_range: NOTE excel does not support this part of t…

…he spec!

examples/example.rb

@@ -342,6 +342,7 @@
   sheet.add_row [4, 5, 6], :style => unlocked # these cells will not!
 end
 
+
 ##Specify page margins and other options for printing
 
 #```ruby

lib/axlsx/util/simple_typed_list.rb

@@ -149,7 +149,7 @@ def #{method}(*args, &block)
 
     def to_xml_string(str = '')
       classname = @allowed_types[0].name.split('::').last
-      el_name = serialize_as || (classname[0,1].downcase + classname[1..-1])
+      el_name = serialize_as.to_s || (classname[0,1].downcase + classname[1..-1])
       str << '<' << el_name << ' count="' << @list.size.to_s << '">'
       @list.each { |item| item.to_xml_string(str) }
       str << '</' << el_name << '>'

lib/axlsx/workbook/worksheet/worksheet.rb

@@ -541,6 +541,11 @@ def to_xml_string
       str.concat '</sheetData>'
       str.concat "<autoFilter ref='%s'></autoFilter>" % @auto_filter if @auto_filter
       @sheet_protection.to_xml_string(str) if @sheet_protection
+      unless @protected_ranges.empty?
+        str << '<protectedRanges>'
+        @protected_ranges.each { |pr| pr.to_xml_string(str) }
+        str << '</protectedRanges>'
+      end
       str.concat "<mergeCells count='%s'>%s</mergeCells>" % [@merged_cells.size, @merged_cells.reduce('') { |memo, obj| memo += "<mergeCell ref='%s'></mergeCell>" % obj } ] unless @merged_cells.empty?
       print_options.to_xml_string(str) if @print_options
       page_margins.to_xml_string(str) if @page_margins