a more idiomatic version of the server

A few small changes to make the code look more idiomatic for the Clojure version of the server.

A few of the things to note are:

* you do not need a `do` block inside the function body, or inside a `let` statement, you would only need to use `do` inside something like `if`
* you don't need to use `str` inside `println` it already accepts n arguments, and it will put spaces between them for you
* you normally use `with-open` to manage IO resources such as streams, it ensures that `close` will be called on the resource when you're done using it
* clojure.java.io already has a `reader` function, so `get-reader` is superfluous