for mac os x set the platform version to only the major and minor and use a max of 10.7 as this is what the omnitruck supports
this commit fixes issue #39 - allow rpm to install older versions of chef-client
Adds chef-client service

Fixes an issue where if restart_chef_service is set to true,
the notification to restart the chef-client service raises an
error that chef-client service is not defined.
Style modification (single quote string)