remove code for 2.6 support

gevent/_socket2.py

@@ -53,10 +53,7 @@ else:
                 if not self.closed:
                     self.close()
 
-if sys.version_info[:2] < (2, 7):
-    _get_memory = buffer
-else:
-    def _get_memory(data):
+def _get_memory(data):
     try:
         mv = memoryview(data)
         if mv.shape: