Fixes authorized_keys file permissions

Owner and group id are not inherit when calling shutil move. This commit
moves setting permissions logic for the authorized_keys file to be sure
that the final destination file has the proper permissions.
fixes #48, account manager was not starting on upstart systems
support both CentOS and Debian derivatives
Merge pull request #49 from erjohnso/master

fixes #48, account manager was not starting on upstart systems
Merge pull request #46 from frodenas/master

Fixes authorized_keys file permissions