Downgrade nrepl.el to 0.2.0

There is no tag for version 0.2.0 right now, but the commit
SHA is 87345bf9e65f85826e0a062fe50ff68e1abd959e

Major changes to the file structure started after that commit,
breaking nrepl-jack-in for me. I'll give it some more time to
stabilize in the new arrangement.
Add symlink to nrepl.el directory

In preparation for upcoming changes to nrepl.el where it is split
into multiple files.

See for example
https://github.com/clojure-emacs/nrepl.el/commit/89174492f4cbeff6f85bf72f0312fd8ff1a53a12