change test command to reflect new package organization

tests/test_hello.py

 import unittest
-from pak.hello import hello
+import pak
 
 class TestMyModule(unittest.TestCase):
     def test_hello(self):
-        self.assertEqual(hello(), "Hello, World!")
+        self.assertEqual(pak.main(), "Hello, World!")
 
 if __name__ == '__main__':
     unittest.main()
\ No newline at end of file