Adapting observe to use smoke (this is built on top of the previous change that

pkg/observe/pubspec.yaml

Index: pkg/observe/pubspec.yaml
diff --git a/pkg/observe/pubspec.yaml b/pkg/observe/pubspec.yaml
index 3b0407c362e92a0f3ff4d7b4a8ed7d9040c38ff1..c98e4dd16983cf0c97a2573a49c1bc48a50c3ad0 100644
--- a/pkg/observe/pubspec.yaml
+++ b/pkg/observe/pubspec.yaml
@@ -13,6 +13,7 @@ dependencies:
   barback: ">=0.9.0 <0.12.0"
   logging: ">=0.9.0 <0.10.0"
   path: ">=0.9.0 <2.0.0"
+  smoke: ">=0.1.0-dev <0.2.0"
   source_maps: ">=0.9.0 <0.10.0"
 dev_dependencies:
   unittest: ">=0.9.0 <0.10.0"