Remove "from __future__ import print"

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

Fixes #652

examples/linearbandwidth.py

@@ -23,7 +23,6 @@ of switches, this example demonstrates:
 
 """
 
-from __future__ import print_function
 
 from mininet.net import Mininet
 from mininet.node import UserSwitch, OVSKernelSwitch, Controller