Add missing include in sky_tool

Also fixed missing entry in CHANGELOG.md

TBR=ianh@google.com

Review URL: https://codereview.chromium.org/1108393003

packages/flutter/CHANGELOG.md

@@ -6,6 +6,10 @@
 
   - Added download_material_design_icons script.
 
+## 0.0.5+dart-summit-3
+
+  - Fix typo in lib/sky_tool causing syntax error when run.
+
 ## 0.0.5+dart-summit-2
 
   - Various demo fixes and added ChangeLogs.

packages/flutter/lib/sky_tool

@@ -7,6 +7,7 @@ import argparse
 import json
 import logging
 import os
+import re
 import signal
 import socket
 import subprocess