Add missing dependencies (#25)

Author: f3ath

pubspec.yaml

@@ -5,8 +5,10 @@ name: "json_api"
 version: "0.1.0"
 dependencies:
   http: "^0.12.0"
+  collection: "^1.14.11"
 dev_dependencies:
   json_matcher: "^0.2.2"
   test: "^1.3.0"
+  stream_channel: "^1.6.8"
 environment:
   sdk: ">=2.0.0 <3.0.0"