New: OJTestCase calls a setUp and tearDown class

Previously, OJTest didn't call a setUp or tearDown class. Now it does.
When launching the test, the methods +(void)setUp will be called once.
When all of the tests are finished, the methods +(void)tearDown will be called once.
Merge pull request #26 from Dogild/SetUpClassTearDownClass

New: OJTestCase calls a setUp and tearDown class