Improve the way middleware is loaded with the clojure command and tools.deps

@SevereOverfl0w noticed the following:

> @bozhidar perchance noticed that https://github.com/clojure-emacs/cider/blob/master/cider.el#L160 seems wrong/different to how boot/lein works. The vector passed to `init` should be the `cider-jack-in-nrepl-middlewares`

I put this hastily together and we should fix it, before shipping 0.17. 