minor changes to organize imports and to the gitignore file

lib/src/packages_io_impl.dart

Index: lib/src/packages_io_impl.dart
diff --git a/lib/src/packages_io_impl.dart b/lib/src/packages_io_impl.dart
index 0e9474639420d7552a6f0d524cfd05f71b161121..9eba9ce44b643c551953bbb6b62f24cea0553be3 100644
--- a/lib/src/packages_io_impl.dart
+++ b/lib/src/packages_io_impl.dart
@@ -8,7 +8,9 @@ library package_config.packages_io_impl;
 
 import "dart:collection" show UnmodifiableMapView;
 import "dart:io" show Directory;
+
 import "package:path/path.dart" as path;
+
 import "packages_impl.dart";
 
 /// A [Packages] implementation based on a local directory.