refactor(dart/transform): Simplify deferred rewriting

Simplify the DeferredRewriting and move package:quiver to a dev
dependency.

Closes #6994

modules/angular2/pubspec.yaml

@@ -18,12 +18,12 @@ dependencies:
   logging: '>=0.9.0 <0.12.0'
   observe: '^0.13.1'
   protobuf: '^0.5.0'
-  quiver: '^0.21.4'
   source_span: '^1.0.0'
   stack_trace: '^1.1.1'
 dev_dependencies:
   code_transformers: '>=0.2.9+4 <0.4.0'
   guinness: '^0.1.18'
+  quiver: '^0.21.4'
   test: '^0.12.6'
 transformers:
 - angular2