Merge pull request flutter#6 from bcko/patch-1

Update .gitignore to new `dart_tool` pub cache

Author: mit-mit

.gitignore

@@ -1,9 +1,8 @@
 # Don’t commit the following directories created by pub.
 .buildlog
-.pub/
-build/
-packages
+.dart_tool/
 .packages
+build/
 
 # Or the files created by dart2js.
 *.dart.js
@@ -12,4 +11,4 @@ packages
 *.js.map
 
 # Include when developing application packages.
-pubspec.lock
+pubspec.lock