Add README.

Author: Arthur Evans

README.md

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+# Polymer Starter Project
+
+This project includes a set of Polymer components and a starter project,
+designed to be used with the [Polymer tutorial](http://polymer-project.org/start/tutorial/intro.html).
+
+In this tutorial, you build a simple client for `unquote`, the read-only social networking service.
+
+
+## Project contents
+
+ -   `starter`. Scaffolding for the starter project. If you're working through the tutorial, start here!
+ -   `step-1` to `step-3`. Intermediate versions of the project. Check your work!
+ -   `finished`. The completed `unquote` app.
+ -   `components`. Selection of Polymer elements used in the project.
+ -   `post-service`. A pre-built element that implements an interface to the `unquote` service. 
+ -   `api`. Data for the the `unquote` service.
+ -   `images`. Avatar images.
+
+Find a problem in the tutorial? Please open a [Doc bug](https://github.com/Polymer/docs/issues/new) so we can fix it.