Add trailing "ends here" line for package.el compatibility

Without this line, package.el pedantically refuses to install this library. (Background: I'm adding a [MELPA](http://melpa.milkbox.net/) recipe for `bdo`)

BTW, you might also be interested in [skewer-mode](https://github.com/skeeto/skewer-mode), which uses a similar approach to yours in order to connect a js repl to a browser.