Update charted to 0.4.8 and roll

packages/when/example/read_json_file.dart

-
-library when.example.read_json_file;
-
-import 'dart:async';
-import 'dart:convert';
-import 'dart:io';
-
-import 'package:when/when.dart';
-
-/// Reads and decodes JSON from [path] asynchronously.
-///
-/// If [path] does not exist, returns the result of calling [onAbsent].
-Future readJsonFile(String path, {onAbsent()}) => _readJsonFile(
-    path, onAbsent, (file) => file.exists(), (file) => file.readAsString());
-
-/// Reads and decodes JSON from [path] synchronously.
-///
-/// If [path] does not exist, returns the result of calling [onAbsent].
-readJsonFileSync(String path, {onAbsent()}) => _readJsonFile(
-    path, onAbsent, (file) => file.existsSync(),
-    (file) => file.readAsStringSync());
-
-_readJsonFile(String path, onAbsent(), exists(File file), read(File file)) {
-  var file = new File(path);
-  return when(
-      () => exists(file),
-      onSuccess: (doesExist) => doesExist ?
-          when(() => read(file), onSuccess: JSON.decode) :
-          onAbsent());
-}
-
-main() {
-  var syncJson = readJsonFileSync('foo.json', onAbsent: () => {'foo': 'bar'});
-  print('Sync json: $syncJson');
-  readJsonFile('foo.json', onAbsent: () => {'foo': 'bar'}).then((asyncJson) {
-    print('Async json: $asyncJson');
-  });
-}