Fix tests for ruby 2.0

This fixes most of the issues I had with the test suite running with Ruby 2.0

There are two outstanding issues:

1. test_example_java_result(KwarkUsersGuideTest) - I really did not investigated the issue
2. test_untabify2(MainTest) - Not sure how to deal with that. It seems that Syck was able to deal with tabs while Psych is not able to handle them by design. Somebody else has to decide.