Import test.base instead of importing unittest. Removed top-level

code -- use testdriver.py to run the tests instead.
(TestSpawn): Inherit from test.base.TestCase.
(TestSpawn.test_spawn_sleep_1): Use assertTimeDiff instead of
	assertAlmostEqual.
(TestSpawn.test_spawn_sleep_1_compat): Ditto.
(TestSpawn.test_hello_world): New test.
(TestSpawn.test_stderr): New test.
(TestSpawn.test_stderr_2): New test.