this is in preparing to move to sqlite as the backend

Other 404s are already logged in their respective handlers.

The path `/` alone is a wildcard, which also matches things like
`/foo`, `/potatoe`, `/yes/this/works/` and such. We don't want that.
Send an HTTP 404 for any path not matched otherwise and not equal to
`/`.

Panic'ing is okay here, since uneven arguments to `.Log` are always a
programming error.

Login is done by clicking the user button in the top right.

`hash` is not really specific.

This prevents re-downloading all sorts of dependencies all the time.

- deploy.sh takes a binary from stdin, moves it to the right place
  and restarts the service
- authorized_keys configures auth for the deployment user
- rc contains the FreeBSD rc script for the service

`logger` is a closure here, so overwriting it on every request isn't a good idea.

It's easier to use and set up than logrus, and the API is a bit nicer
(no distinction between a logger and a log entry, for example).

This way, failed authentication also has a request ID and such

If a commit fails, we return its error as the error of the function that called it.