re-introduce compatibility attributes on collection nodes to keep compatible with code like::

def pytest_collect_file(path, parent):
        ... parent.Module(...)

--HG--
branch : trunk

setup.py

@@ -22,7 +22,7 @@ def main():
         name='pytest',
         description='py.test: simple powerful testing with Python',
         long_description = long_description,
-        version='2.0.0.dev8',
+        version='2.0.0.dev9',
         url='http://pytest.org',
         license='MIT license',
         platforms=['unix', 'linux', 'osx', 'cygwin', 'win32'],