Fix loading shared strings from namespaced xml

lib/simple_xlsx_reader/loader/shared_strings_parser.rb

@@ -22,7 +22,7 @@ def initialize
 
       attr_reader :result
 
-      def start_element(name, _attrs = [])
+      def start_element_namespace(name, attrs = [], _prefix, _uri, _ns)
         case name
         when 'si' then @current_string = +"" # UTF-8 variant of String.new
         when 't' then @extract = true
@@ -35,7 +35,7 @@ def characters(string)
         @current_string << string
       end
 
-      def end_element(name)
+      def end_element_namespace(name, _prefix, _uri)
         case name
         when 't' then @extract = false
         when 'si' then @result << @current_string

test/shared_strings_namespaced.xml

@@ -0,0 +1 @@
+<?xml version="1.0" encoding="utf-8"?><x:sst xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main"><x:si><x:t>Shared 1</x:t></x:si><x:si><x:t>Shared 2</x:t></x:si><x:si><x:t>Shared 3</x:t></x:si></x:sst>

test/simple_xlsx_reader_test.rb

@@ -639,6 +639,18 @@
       end
     end
 
+    describe 'namespaced shared_strings' do
+      let(:xml) do
+        File.open(File.join(File.dirname(__FILE__), 'shared_strings_namespaced.xml'))
+      end
+
+      let(:ss) { SimpleXlsxReader::Loader::SharedStringsParser.parse(xml) }
+
+      it 'parses strings into a list' do
+        _(ss).must_equal ['Shared 1', 'Shared 2', 'Shared 3']
+      end
+    end
+
     describe 'style_types' do
       let(:xml_file) do
         File.open(File.join(File.dirname(__FILE__), 'styles.xml'))