Update setup.py to reflect that Python 2.6 is no longer supported, but

3.4 is.

setup.py

@@ -89,9 +89,9 @@ setup(name='dulwich',
       classifiers=[
           'Development Status :: 4 - Beta',
           'License :: OSI Approved :: GNU General Public License v2 or later (GPLv2+)',
-          'Programming Language :: Python :: 2.6',
           'Programming Language :: Python :: 2.7',
           'Programming Language :: Python :: 3.4',
+          'Programming Language :: Python :: 3.5',
           'Programming Language :: Python :: Implementation :: CPython',
           'Programming Language :: Python :: Implementation :: PyPy',
           'Operating System :: POSIX',