Doc review: turn "running tests on nose" section into a unittest section

At its core, what's really important to get accross is that an Avocado test
is compatible with unittest.TestCase, and it can be run with compatible
test runners.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

docs/source/WritingTests.rst

@@ -260,14 +260,13 @@ Executing an Avocado test gives::
     INTERRUPT : 0
     TIME      : 1.00 s
 
-Running tests with nosetests
-============================
+Running tests under other :mod:`unittest` runners
+-------------------------------------------------
+
+`nose <https://nose.readthedocs.org/>`__ is another Python testing framework
+that is also compatible with :mod:`unittest`.
 
-`nose <https://nose.readthedocs.org/>`__ is a Python testing framework with
-similar goals as Avocado, except that avocado also intends to provide tools to
-assemble a fully automated test grid, plus richer test API for tests on the
-Linux platform. Regardless, the fact that an Avocado class is also an unittest
-cass, you can run them with the ``nosetests`` application::
+Because of that, you can run avocado tests with the ``nosetests`` application::
 
     $ nosetests examples/tests/sleeptest.py
     .
@@ -276,6 +275,28 @@ cass, you can run them with the ``nosetests`` application::
 
     OK
 
+Conversely, you can also use the standard :func:`unittest.main` entry point to run an
+Avocado test. Check out the following code, to be saved as ``dummy.py``::
+
+   from avocado import Test
+   from unittest import main
+
+   class Dummy(Test):
+       def test(self):
+           self.assertTrue(True)
+
+   if __name__ == '__main__':
+       main()
+
+It can be run by::
+
+   $ python dummy.py
+   .
+   ----------------------------------------------------------------------
+   Ran 1 test in 0.000s
+
+   OK
+
 Setup and cleanup methods
 =========================