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

code -- use testdriver.py to run the tests instead.
(TestPopen): Inherit from test.base.TestCase.
(Timeout): Moved to test/base.py.
(handler): Ditto.
(TestPopen.setUp): Moved to test.base.TestCase.
(TestPopen.tearDown): Ditto.
(TestPopen.test_popen_sleep_1): Use assertTimeDiff instead of
	assertAlmostEqual.
(TestPopen.test_popen_sleep_1_compat): Ditto.
(TestPopen.test_read_hello_no_eof_handling): New test.
(TestPopen.test_read_hello_no_eof_handling_no_exception): New test.