use python2.7 and not python2 (OSX compatibility)

start.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python2.7
 
 
 # Included modules

zeronet.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python2.7
 
 # Included modules
 import os