Remove ununsed params in params.pp, update creates to unless

pip2pi in the cache_server.pp was a hard coded link, and the "creates" command was incorrect for Debian. This was updated with a more globally scoped path, and a "which app" unless check rather than a pointed creates which
seems to have a potential to change.
Merge pull request #8 from robertstarmer/modify_pip2pi_params

Modify pip2pi path and params