enhance `cider-connect` to auto-detect running repls on local and remote hosts

 - `cider-connect` now interactively asks for host from a combined list of hosts
   from machine-wide ssh configuration, `cider-known-endpoints`.

 - Once the host has been selected `cider-connect` locates running instances of
   lein servers. The machine must have `ps` and `grep` programs in the bin path.