setup.py: update download url and remove python 2.6 support (#508)

Author: thiell

setup.py

@@ -67,9 +67,8 @@
       author='Stephane Thiell',
       author_email='[email protected]',
       license='LGPLv2+',
-      url='http://clustershell.sourceforge.net/',
-      download_url='http://sourceforge.net/projects/clustershell/files/'
-                   'clustershell/%s/' % VERSION,
+      url='https://clustershell.readthedocs.io/',
+      download_url='https://github.com/cea-hpc/clustershell/archive/refs/tags/v%s.tar.gz' % VERSION,
       platforms=['GNU/Linux', 'BSD', 'MacOSX'],
       keywords=['clustershell', 'clush', 'clubak', 'nodeset'],
       description='ClusterShell library and tools',
@@ -83,7 +82,6 @@
           "Operating System :: POSIX :: BSD",
           "Operating System :: POSIX :: Linux",
           "Programming Language :: Python",
-          "Programming Language :: Python :: 2.6",
           "Programming Language :: Python :: 2.7",
           "Programming Language :: Python :: 3",
           "Topic :: Software Development :: Libraries :: Python Modules",