Make tests compatible with Ruby 1.9.2

When I tried to run the tests on 1.9.2 I ran into serveral loading issues.

I've made some changes to fix this, see diff. Please note: redgreen relies on some test-unit runner that comes not bundled with Ruby anymore. I followed the simplest possible solution and just removed it.

Ruby 1.9.2-p290

    Loaded suite /Users/rmoriz/.rbenv/versions/1.9.2-p290/bin/rake
    Started
    .................................
    Finished in 78.063048 seconds.
    
    33 tests, 52 assertions, 0 failures, 0 errors, 0 skips


REE 1.8.7-2011.03

    Loaded suite /Users/rmoriz/.rbenv/versions/ree-1.8.7-2011.03/bin/rake
    Started
    .................................
    Finished in 93.586207 seconds.

    33 tests, 52 assertions, 0 failures, 0 errors
    

Ruby 1.8.7-p352

    33 tests, 52 assertions, 0 failures, 0 errors

    Loaded suite /Users/rmoriz/.rbenv/versions/1.8.7-p352/bin/rake
    Started
    .................................
    Finished in 80.367684 seconds.
    
    33 tests, 52 assertions, 0 failures, 0 errors


Ruby 1.9.3-p0

    Run options: 
    
    # Running tests:
    
    .........................../Users/rmoriz/.rbenv/versions/1.9.3-p0/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': iconv will be deprecated in the future, use String#encode instead.
    ......
    
    Finished tests in 77.889838s, 0.4237 tests/s, 0.6676 assertions/s.
    
    33 tests, 52 assertions, 0 failures, 0 errors, 0 skips