Added support for greater configuration of unix_http_server

Added three params to supervisor class

    unix_server_file    (default: /var/run/supervisor.sock)
    unix_server_chmod   (default: undef)
    unix_server_chown   (default: undef)

Example of use:

    class {'supervisor':
      unix_server_chmod => '0770',
      unix_server_chown => 'root:admin',
    }

Users belonging to 'admin' group are then able to interact with supervised
processes without resorting to sudo.
Fix restarting problems

when both supervisord.conf and managed services configs changed

Also fixes plathrop/puppet-module-supervisor#62
Narrow logfile dependency to logdir instead of entire class
Apply PR#48
Merge remote-tracking branch 'upstream/pr/69'
Merge remote-tracking branch 'upstream/pr/71'