Added the default WET theme

This is what you folks were waiting for I hear? (@pjackson28, @nschonni, @patheard @cfarquharson @masterbee )

Note that this is mostly a shell. The mobile view is a more robust than the mobile view (mobile first right). However the stage is set for everything. There are working functions for transition from large to medium/small view, There's the template with some i18n and a lot more.

Here's what need to be done
* Add mixins to the medium/small view (@nschonni can you help with this)
* Completely redo the large view. This will require both CSS and JavaScript knowledge to perform the right transition of the DOM to and from the large view as well as the styles. (@patheard and @cfarquharson are you interested?)
* Finish the i18n of the theme (@nschonni is working on a grunt task to output the json files but we need to add the values in the theme
* Split the theme into includes
* Create custom handlebars helpers for common elements like breadcrumbs etc

There's probably a lot more to do but that's a good start. If you have any question let me know.

P.S. the root example doesn't work because of a bug in assemble that we are working on resolving.