Copy all of dart_sky.dart's supporting files into package:sky

Also bumped package:sky's version in prep for publishing.

R=abarth@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1024243002

packages/flutter/CHANGELOG.md

+## 0.0.2
+
+  - sdk_additions now includes previously missing imports.
+  - added lib/sky_tool, and supporting apks/SkyDemo.apk

packages/flutter/pubspec.yaml

@@ -2,6 +2,6 @@ name: sky
 author: Chromium Authors <sky-dev@googlegroups.com>
 description: Dart files to support executing inside Sky.
 homepage: https://github.com/domokit/mojo/tree/master/sky
-version: 0.0.1
+version: 0.0.2
 dependencies:
   mojo: '>=0.0.1 <1.0.0'