Add test for custom markup engine

This required adding a file to the example repo, so some of the tests'
expected hash values changed accordingly.

test/test_page.rb

@@ -236,4 +236,18 @@ if $METADATA
   end
 end
 
+end
+
+context "with custom markup engines" do
+  setup do
+    Gollum::Markup.register(:redacted, "Redacted", :regexp => /rd/) { |content| content.gsub /\S/, '-' }
+    @wiki = Gollum::Wiki.new(testpath("examples/lotr.git"))
+  end
+
+  test "should use the specified engine" do
+    page = @wiki.page('Riddles')
+    assert_equal :redacted, page.format
+    assert page.raw_data.include? 'Time'
+    assert page.raw_data =~ /^[\s\-]*$/
+  end
 end