Add README.txt docs, remove obsolete unittest.py

lib/python/Testing/README.txt

+The Testing package is a set of shared routines for the Zope unit
+testing framework.   To add a test suite to a Zope package:
+
+1. Make a 'tests' subdirectory.
+
+2. Copy 'framework.py' into 'tests' from any other package's 'tests'.
+
+Once a test suite has been set up, you can add test modules:
+
+1. Create a file with a name matching 'test*.py'.
+
+2. Define one or more subclasses of 'unittest.TestCase'.  The unittest
+   module is imported by the framework.
+
+3. Define methods for the test classes.  Each method's name must start
+   with 'test'.  It should test one small case, using a Python
+   'assert' statement.  Here's a minimal example:
+
+   class testClass1(unittest.TestCase):
+       def testAddition(self):
+           assert 1 + 1 == 2, 'Addition failed!'
+
+4. You can add 'setUp' and 'tearDown' methods that are automatically
+   called at the start and end of the test suite.
+
+5. Follow the instructions in 'framework.py' about adding lines to the
+   top and bottom of the file.
+
+Now you can run the test as "python path/to/tests/testName.py", or
+simply go to the 'tests' directory and type "python testName.py".