Update start.js route handler

* Lower the maximum for `prefix`
* Add in defaults when query param key exists but value does not exist
* Update CSS generation code
minor updates to shared templates
add handlebars runtime JS
initial drop of Y.GridModel and Y.MqModelList
initial drop of Y.GridInputView, and Y.GridOutputView
initial drop of Y.GridRouter
update grid-input-view with error handling & prefix input
add new modules to YUI config
add error-handling code to start.css
set up client-side app
pass in query params to res.locals for download button
add <aside> link for downloading zip file
remove grid-router, add requires
remove grid-router subclass
beef up grid-model with stringify() method, attribute validations
Change architecture so that views directly manipulate model.

Instead of classical MVC, the views directly update the model.
The router in start.js listens for model change events and updates
the route, which triggers a view.render()
remove duplicated handlebars-runtime dependency
add HTML5 form validation
minor tweaks to CSS and DOM
remove empty query param check