Add tasks for all the new languages

Task/Tree-traversal/Ceylon/tree-traversal.ceylon

@@ -0,0 +1,97 @@
+import ceylon.collection {
+	ArrayList
+}
+
+shared void run() {
+
+	class Node(label, left = null, right = null) {
+		shared Integer label;
+		shared Node? left;
+		shared Node? right;
+		string => label.string;
+	}
+	
+	void preorder(Node node) {
+		process.write(node.string + " ");
+		if(exists left = node.left) {
+			preorder(left);
+		}
+		if(exists right = node.right) {
+			preorder(right);
+		}
+	}
+	
+	void inorder(Node node) {
+		if(exists left = node.left) {
+			inorder(left);
+		}
+		process.write(node.string + " ");
+		if(exists right = node.right) {
+			inorder(right);
+		}
+	}
+	
+	void postorder(Node node) {
+		if(exists left = node.left) {
+			postorder(left);
+		}
+		if(exists right = node.right) {
+			postorder(right);
+		}
+		process.write(node.string + " ");
+	}
+	
+	void levelOrder(Node node) {
+		value nodes = ArrayList<Node> {node};
+		while(exists current = nodes.accept()) {
+			process.write(current.string + " ");
+			if(exists left = current.left) {
+				nodes.offer(left);
+			}
+			if(exists right = current.right) {
+				nodes.offer(right);
+			}
+		}
+	}
+
+	value tree = Node {
+		label = 1;
+		left = Node {
+			label = 2;
+			left = Node {
+				label = 4;
+				left = Node {
+					label = 7;
+				};
+			};
+			right = Node {
+				label = 5;
+			};
+		};
+		right = Node {
+			label = 3;
+			left = Node {
+				label = 6;
+				left = Node {
+					label = 8;
+				};
+				right = Node {
+					label = 9;
+				};
+			};
+		};
+	};
+	
+	process.write("preorder:   ");
+	preorder(tree);
+	print("");
+	process.write("inorder:    ");
+	inorder(tree);
+	print("");
+	process.write("postorder:  ");
+	postorder(tree);
+	print("");
+	process.write("levelorder: ");
+	levelOrder(tree);
+	print("");
+}