one-click Heroku deploy support

So this is semi/totally bullshit, but I figured I'd open the PR for the purpose of further conversation.

The primary problem is (I think) the vendoring of `bindata.go`. Obviously idomatic go provides no guidance on how to manage an asset pipeline today, and the popular `kr` https://github.com/kr/heroku-buildpack-go buildpack doesn't know about how to use your Makefile.

Adding a `Procfile`, `app.json` and vendoring godeps all seem more-or-less reasonable to me.

Oh, I also stopped checking if there were any tables and crashing if not. `pgweb` should probably work on empty databases. I mean... why not?

A logo which isn't your picture for the app.json would be cool too, but with this branch you can hit the `deploy` button and get a working app.