conditionally install unittest2 only for python 2.6

setup.py

@@ -1,4 +1,5 @@
 import setuptools
+import sys
 
 version = '4.0.dev'
 shortdesc = 'iCalendar parser/generator'
@@ -6,7 +7,10 @@ longdesc = open('README.rst').read()
 longdesc += open('CHANGES.rst').read()
 longdesc += open('LICENSE.rst').read()
 
-tests_require = ['unittest2']
+tests_require = []
+if sys.version_info[:2] == (2, 6):
+    # Python unittest2 only needed for Python 2.6
+    tests_require = ['unittest2']
 
 setuptools.setup(
     name='icalendar',
@@ -16,6 +20,11 @@ setuptools.setup(
     classifiers=[
         'Development Status :: 5 - Production/Stable',
         'Intended Audience :: Developers',
+        "Programming Language :: Python",
+        "Programming Language :: Python :: 2.6",
+        "Programming Language :: Python :: 2.7",
+        "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.3",
         'License :: OSI Approved :: BSD License',
         'Operating System :: OS Independent',
         ],
@@ -36,4 +45,5 @@ setuptools.setup(
     ],
     extras_require={
         'test': tests_require
-    })
+    }
+)