Better server-side rendering with Handlebars

@redfieldstefan, here's more progress on the server-side rendering!

If you've POSTed drinks into your database, this should still render their pages--you'd find "Gin and Tonic" at `cocktails/gin-and-tonic`, for example.

Note that this version isn't using React anymore, just a templating language called Handlebars. I'm thinking that might be enough for our needs.

Also note that Handlebars lets us separate our DOM components a little, and reuse some. We can define a block of HTML in `views/partials` as the side nav, and use it elsewhere without repeating ourselves.
Cf. https://github.com/redfieldstefan/mixandstones/commit/40eb0cffcaa383a6d1276ae501d9e0c3fef415c9

Next step: think about porting *all* the HTML into Handlebars templates, and shifting new front-end work (e.g., CSS) there too.