Parallel tests

This looks to be happy now, building fine both locally and on the jenkins box. I would appreciate if other developers could run the test suite in parallel on their machines so we can give it a thorough run out. There is a new rake task that does all the appropriate setup and runs the entire suite: `rake test:in_parallel`.

By default, parallel_test will use all available processors. You can override this by settings the `PARALLEL_TEST_PROCESSORS` environment variable.