use shared code transformer, update web_components to remove .map and .concat files

pkg/web_components/pubspec.yaml

 name: web_components
-version: 0.9.0
+version: 0.9.0+1
 author: Polymer.dart Authors <web-ui-dev@dartlang.org>
 homepage: https://www.dartlang.org/polymer-dart/
 description: >
   Polyfills for Shadow DOM, Custom Elements, and HTML Imports.
   Custom Elements let authors define their own elements. Authors associate code
   with custom tag names, and then use those custom tag names as they would any
   standard tag. Shadow DOM is designed to provide encapsulation for custom
   elements, by hiding DOM subtrees under shadow roots. HTML Imports let authors
   bundle code and HTML as if they were libraries.
 environment:
   sdk: ">=1.4.0-dev.6.6 <2.0.0"
+dependencies:
+  code_transformers: ">=0.2.2 <0.3.0"
+transformers:
+# TODO(sigmund): once we have some easier way to do global app-level
+# transformers, we might want to remove this transformer here and only apply it
+# in apps that need it.
+- code_transformers/src/delete_file:
+    $include:
+      - lib/platform.concat.js
+      - lib/platform.concat.js.map
+      - lib/platform.js.map
+- code_transformers/src/remove_sourcemap_comment:
+    $include: lib/platform.js