implement Page.version

test/test_page.rb

@@ -17,6 +17,7 @@ context "Page" do
     assert page.raw_data =~ /^# Bilbo Baggins\n\nBilbo Baggins/
     assert page.formatted_data =~ /<h1>Bilbo Baggins<\/h1>\n\n<p>Bilbo Baggins/
     assert_equal :markdown, page.format
+    assert_equal 'df26e61e707116f81ebc6b935ec6d1676b7e96c4', page.version.id
   end
 
   test "no page match" do