Polymer/paper-spinner — pull request #10 by aghassemi (2014-11-21 18:13:47+00:00)
Title: Adding accessibility support

Adds aria role of ```progressbar``` and exposes an ```alt``` attribute that will be used as ```aria-label```.
```alt``` defaults to ```loading``` if not specified, not great for internationalization but in my opinion better than the alternative which would make it hidden from screen readers.
Also setting ```aria-hidden``` when active state changes.