curds: Begin implementing a PlaylistNode

My intention is to try to match the GtkTreeModel interface in terms of
functionality. This way, each node can act as its own iterator.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

curds/playlist/node.py

@@ -0,0 +1,9 @@
+# Copyright 2019 (c) Anna Schumaker.
+
+class PlaylistNode:
+    def __init__(self, name="", icon=""):
+        self.children = [ ]
+        self.icon     = icon
+        self.name     = name
+        self.next     = None
+        self.prev     = None

curds/playlist/test_node.py

@@ -0,0 +1,16 @@
+# Copyright 2019 (c) Anna Schumaker.
+from . import node
+import unittest
+
+class TestPlaylistNode(unittest.TestCase):
+    def test_node_init(self):
+        n = node.PlaylistNode()
+        self.assertEqual( n.children, [ ])
+        self.assertEqual( n.icon, "")
+        self.assertEqual( n.name, "")
+        self.assertIsNone(n.next)
+        self.assertIsNone(n.prev)
+
+        n = node.PlaylistNode("Test Node", "test-icon")
+        self.assertEqual(n.icon, "test-icon")
+        self.assertEqual(n.name, "Test Node")