Roll to v15 for republishing with skyx enabled

TBR=abarth@google.com

Review URL: https://codereview.chromium.org/1222193008 .

sdk/CHANGELOG.md

+## 0.0.15
+
+  - 6 changes: https://github.com/domokit/mojo/compare/4df2d39...e028733
+
 ## 0.0.14
 
   - 42 changes: https://github.com/domokit/mojo/compare/3de9766...cf84c48

sdk/example/demo_launcher/apk/AndroidManifest.xml

@@ -3,7 +3,7 @@
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file.
  -->
-<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="org.domokit.sky.demo" android:versionCode="14" android:versionName="0.0.14">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="org.domokit.sky.demo" android:versionCode="15" android:versionName="0.0.15">
 
     <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="21" />
     <uses-permission android:name="android.permission.INTERNET" />

sdk/pubspec.yaml

@@ -7,4 +7,4 @@ dependencies:
 description: Dart files to support executing inside Sky.
 homepage: https://github.com/domokit/mojo/tree/master/sky
 name: sky
-version: 0.0.14
+version: 0.0.15