add cider nrepl support

the latest version of the cider uses [cider/cider-nrepl "0.8.0-snapshot"], which breaks the nrepl support for lein-ring, this pull request fixes the breakage. to use [cider/cider-nrepl "0.8.0-snapshot"], one has to:

git clone git@github.com:clojure-emacs/cider-nrepl.git
lein install

then introduce it into the project.clj  or ~/.lein/profiles.clj