Update CHANGELOGs for pub packages on trunk

TBR=hansmuller@chromium.org

Review URL: https://codereview.chromium.org/1082413002

packages/flutter/CHANGELOG.md

+## 0.0.5+dart-summit-2
+
+  - Various demo fixes and added ChangeLogs.
+
+
+## 0.0.5+dart-summit-1
+
+  - Branched from mojo trunk to stabalize for Dart summit.
+
+
 ## 0.0.2
 
   - sdk_additions now includes previously missing imports.