Merge pull request #22 from ericf/get-started-server

Simplify /start/ route and add proper error checking
share pure grid config between client and server
remove demo and observer templates. no longer needed
update start.handlebars documentation with new responsive grid partials
update CSS to reflect start.handlebars changes
remove .content from `div.grid-input`
Add `.is-code-full` style rules for full-width code blocks
Simplify the code for showing selected Grids media queries on /start/