Fall back to xmlGetProp when an attribute namespace cannot be found.

This allows us to find namespaced properties in HTML documents.
Fixes #861.

ext/nokogiri/xml_node.c

@@ -753,6 +753,8 @@ static VALUE get(VALUE self, VALUE rattribute)
     ns = xmlSearchNs(node->doc, node, (const xmlChar *)(prefix));
     if (ns) {
       value = xmlGetNsProp(node, (xmlChar*)(attr_name), ns->href);
+    } else {
+      value = xmlGetProp(node, (xmlChar*)StringValuePtr(rattribute));
     }
   } else {
     value = xmlGetNoNsProp(node, (xmlChar*)attribute);

test/html/test_node.rb

@@ -34,6 +34,14 @@ def test_get_attribute
         assert_match(/%22AGGA-KA-BOO!%22/, element.to_html)
       end
 
+      # The HTML parser ignores namespaces, so even properly declared namespaces
+      # are treated as as undeclared and have to be accessed via prefix:tagname
+      def test_ns_attribute
+        html = '<i foo:bar="baz"></i>'
+        doc = Nokogiri::HTML(html)
+        assert_equal 'baz', (doc%'i')['foo:bar']
+      end
+
       def test_css_path_round_trip
         doc = Nokogiri::HTML(File.read(HTML_FILE))
         %w{ #header small div[2] div.post body }.each do |css_sel|