Fix the book build script, and regenerate the book (add to*Case note)

scripts/convert_book.dart

 #!/usr/bin/env dart
 
 import 'dart:io';
-import 'dart:async';
+import 'package:path/path.dart' as path;
 
 Directory outputDir;
 
 String frontMatter(title) {
   final yaml = """
 ---
 # WARNING: GENERATED FILE. DO NOT EDIT.
 # WANT TO CONTRIBUTE? SEE https://github.com/dart-lang/dart-up-and-running-book
 layout: book
 title: "${title} from Dart: Up and Running"
 description: "Read ${title} of Dart: Up and Running, published by O'Reilly."
 ---
 """;
   return yaml;
 }
 
 convertFile(String fileName) {
   print(fileName);
   var file = new File(fileName);
   var contents = file.readAsStringSync();
   var title = new RegExp(r'<title>(.*)</title>').firstMatch(contents)[1];
   var start = contents.indexOf(r'<div class="navheader">');
   var end = contents.lastIndexOf(r'</body></html>');
   var body = contents.substring(start, end);
-  var filenameOnly = new Path(fileName).filename;
+  var filenameOnly = path.basename(fileName);
 
   writeFile(filenameOnly, title, body);
 }
 
 writeFile(String fileName, String title, String body) {
   var out = new File('${outputDir.path}/${fileName}');
   out.writeAsStringSync(frontMatter(title));
-  out.writeAsStringSync(body, mode: FileMode.APPEND, encoding: Encoding.UTF_8);
+  out.writeAsStringSync(body, mode: FileMode.APPEND);
 }
 
 checkDir(Directory dir) {
   if (!dir.existsSync()) {
     print("Directory '${dir.path}' does not exist");
     exit(1);
   }
 }
 
 main() {
   var args = new Options().arguments;
   if (args.length != 2) {
     print("Usage: convert_book.dart dir_of_html output_dir");
     exit(1);
   }
 
   var inputDir = new Directory(args[0]);
   outputDir = new Directory(args[1]);
   checkDir(inputDir);
   checkDir(outputDir);
 
   List<FileSystemEntity> filenames = inputDir.listSync();
   filenames
       .map((f) => f.path)
       .where((name) => name.endsWith(".html"))
       .forEach((name) => convertFile(name));
-}
+}