build(pubspec): Clean up pubspec files

Add a direct dependency on package:path.
Remove dependency on package:quiver

modules/angular2/pubspec.yaml

@@ -17,6 +17,7 @@ dependencies:
   intl: '^0.12.4'
   logging: '>=0.9.0 <0.12.0'
   observe: '^0.13.1'
+  path: '^1.0.0'
   protobuf: '^0.5.0'
   source_span: '^1.0.0'
   stack_trace: '^1.1.1'