Rename node.RYU to node.Ryu

Perhaps it should be RyuController, but just Ryu for now.
RYU made no sense because it's not an acronym.

bin/mn

@@ -25,7 +25,7 @@ from mininet.cli import CLI
 from mininet.log import lg, LEVELS, info, debug, warn, error
 from mininet.net import Mininet, MininetWithControlNet, VERSION
 from mininet.node import ( Host, CPULimitedHost, Controller, OVSController,
-                           RYU, NOX, RemoteController, findController,
+                           Ryu, NOX, RemoteController, findController,
                            DefaultController,
                            UserSwitch, OVSSwitch, OVSBridge,
                            IVSSwitch )
@@ -76,7 +76,7 @@ CONTROLLERS = { 'ref': Controller,
                 'ovsc': OVSController,
                 'nox': NOX,
                 'remote': RemoteController,
-                'ryu': RYU,
+                'ryu': Ryu,
                 'default': DefaultController,  # Note: replaced below
                 'none': lambda name: None }
 

mininet/node.py

@@ -38,7 +38,7 @@ OVSController: The test controller from Open vSwitch.
 
 NOXController: a controller node using NOX (noxrepo.org).
 
-RYU: The Ryu controller.
+Ryu: The Ryu controller (https://osrg.github.io/ryu/)
 
 RemoteController: a remote controller node, which may use any
     arbitrary OpenFlow-compatible controller, and which is not
@@ -1447,7 +1447,7 @@ class NOX( Controller ):
                              cdir=noxCoreDir,
                              **kwargs )
 
-class RYU( Controller ):
+class Ryu( Controller ):
     "Controller to run Ryu application"
     def __init__( self, name, *ryuArgs, **kwargs ):
         """Init.