Add code comment to setup.py re: setup() arguments.

setup.py

@@ -75,8 +75,16 @@ import sys
 
 py_version = sys.version_info
 
-# Distribute works with Python 2.3.5 and above:
+# distutils does not seem to support the following setup() arguments.
+# It displays a UserWarning when setup() is passed those options:
+#
+#  * entry_points
+#  * install_requires
+#
+# distribute works with Python 2.3.5 and above:
+#
 #   http://packages.python.org/distribute/setuptools.html#building-and-distributing-packages-with-distribute
+#
 if py_version < (2, 3, 5):
     # TODO: this might not work yet.
     import distutils as dist