Changes to repl task option handling

- The -m/--middleware option can take namespaced symbols. These are
  resolved by the repl-server code. These symbols may refer to vars that
  contain vectors of symbols which will also be resolved.

  See the cider nrepl middleware for an example:
  https://github.com/clojure-emacs/cider-nrepl/blob/v0.7.0/src/cider/nrepl.clj#L14-L25