Working on examples.

Added new example to create xterms.
Other minor changes.

examples/treeInteract.py

@@ -0,0 +1,14 @@
+#!/usr/bin/python
+
+"""Create a tree network and run the CLI on it."""
+
+from mininet import init, TreeNet, Cli
+
+def treeInteract():
+   network = TreeNet( depth=2, fanout=4, kernel=True )
+   network.run( Cli )
+      
+if __name__ == '__main__':
+   init()
+   treeInteract()
+