Changed: uninstalling CouchDB also uninstall its dependencies

This **partly** (see comment below) fixes #108.
Here is the list of Couch dependencies: http://docs.couchdb.org/en/latest/install/unix.html#dependencies

I found Erlang the only one noticeable but if you think other should be uninstalled too, let me know. If it's okay then the issue is **fully** fixed.