Fix an error in README and improve the examples

README

@@ -39,23 +39,19 @@ A simple example which associates CIDR prefixes with strings::
     >>> t = SubnetTree.SubnetTree()
     >>> t["10.1.0.0/16"] = "Network 1"
     >>> t["10.1.42.0/24"] = "Network 1, Subnet 42"
-    >>> t["10.2.0.0/16"] = "Network 2"
+    >>> print "10.1.42.1" in t
+    True
     >>> print t["10.1.42.1"]
     Network 1, Subnet 42
     >>> print t["10.1.43.1"]
     Network 1
-    >>> print "10.1.42.1" in t
-    True
-    >>> print "10.1.43.1" in t
-    True
     >>> print "10.20.1.1" in t
     False
-    >>> print t["10.20.1.1"]
-    Traceback (most recent call last):
-      File "<stdin>", line 1, in <module>
-      File "SubnetTree.py", line 67, in __getitem__
-        def __getitem__(*args): return _SubnetTree.SubnetTree___getitem__(*args)
-    KeyError: '10.20.1.1'
+    >>> try:
+    ...     print t["10.20.1.1"]
+    ... except KeyError, err:
+    ...     print "Error: %s not found" % err
+    Error: '10.20.1.1' not found
 
 By default, CIDR prefixes and IP addresses are given as strings.
 Alternatively, a ``SubnetTree`` object can be switched into *binary
@@ -67,7 +63,7 @@ binary strings as, e.g., returned by `socket.inet_aton
     >>> t.get_binary_lookup_mode()
     False
     >>> t.set_binary_lookup_mode(True)
-    >>> t.binary_lookup_mode()
+    >>> t.get_binary_lookup_mode()
     True
     >>> import socket
     >>> print t[socket.inet_aton("10.1.42.1")]