added additional docs to Node to reduce confusion noted in #73

kademlia/node.py

@@ -3,7 +3,21 @@ import heapq
 
 
 class Node:
+    """
+    Simple object to encapsulate the concept of a Node (minimally an ID, but
+    also possibly an IP and port if this represents a node on the network).
+    This class should generally not be instantiated directly, as it is a low
+    level construct mostly used by the router.
+    """
     def __init__(self, node_id, ip=None, port=None):
+        """
+        Create a Node instance.
+
+        Args:
+            node_id (int): A value between 0 and 2^160
+            ip (string): Optional IP address where this Node lives
+            port (int): Optional port for this Node (set when IP is set)
+        """
         self.id = node_id  # pylint: disable=invalid-name
         self.ip = ip  # pylint: disable=invalid-name
         self.port = port