Upgrading CiviHR to 1.6.8
CiviHR isn't a normal extension that you can install on a general purpose CiviCRM installation.  It is intended to be run as a dedicated CiviHR system and is only supported on Drupal.   

There is a new site at https://civihr.org/ and wiki at https://civihr.atlassian.net/wiki/display/CIV/Welcome

There is a lot of development activity ongoing and some of the docs are lagging behind.  I think they are still offering free hosting if you join the Early Adopters program and meet certain requirements.