Adding demo and sampler scaffold

![screen shot 2014-07-04 at 9 55 01 pm](https://cloud.githubusercontent.com/assets/654526/3485784/90753698-0400-11e4-9ca2-738a66bb3e92.png)

So far we have ported to Dart the polymer elements in the examples to illustrate especially how things interoperate with Dart.

Could we port this one?