Update charted to 0.4.8 and roll

packages/which/lib/src/which_impl.dart

-
-library which.src.which_impl;
-
-import 'dart:async';
-
-import 'package:when/when.dart';
-
-import 'util.dart';
-
-Future<String> which(
-    String command,
-    Iterable<String> candidatePaths,
-    bool isWindows,
-    Future<bool> isExecutable(String path, bool isWindows),
-    orElse()) => new Future(() => _which(
-    command,
-    candidatePaths,
-    isWindows,
-    isExecutable,
-    orElse,
-    toSequence: (items) => new Stream.fromIterable(items)));
-
-String whichSync(
-    String command,
-    Iterable<String> candidatePaths,
-    bool isWindows,
-    bool isExecutable(String path, bool isWindows),
-    orElse()) => _which(
-    command,
-    candidatePaths,
-    isWindows,
-    isExecutable,
-    orElse);
-
-_which(
-    String command,
-    Iterable<String> candidatePaths,
-    bool isWindows,
-    isExecutable(String path, bool isWindows),
-    orElse(),
-    {toSequence(Iterable items): identity}) => when(
-    () => firstWhere(
-        toSequence(candidatePaths),
-        (path) => isExecutable(path, isWindows),
-        orElse: orElse != null ? orElse : () => _commandNotFound(command, null)),
-    onError: (e) => _commandNotFound(command, e));
-
-_commandNotFound(String command, e) {
-  var message = 'Command not found: $command';
-  if (e != null) message += '\n$e';
-  throw new StateError(message);
-}