Remove "from __future__ import print"

This was well-intentioned, but it causes more trouble
than it's worth.

Fixes #652

mininet/cli.py

@@ -25,7 +25,6 @@ list all nodes ('nodes'), to print out the network topology
 and bandwidth ('iperf'.)
 """
 
-from __future__ import print_function
 from subprocess import call
 from cmd import Cmd
 from os import isatty

mininet/util.py

@@ -1,6 +1,5 @@
 "Utility functions for Mininet."
 
-from __future__ import print_function
 
 from mininet.log import output, info, error, warn, debug