Enhance validation of sensu_check resources
Enhance validation of sensu_check resources

Cherry-picked from #396, closes #396

* Adds validation of check names
* Ensures presense of `standalone` or `subscribers` attributes

cwjohnston/sensu-chef,sensu/sensu-chef,klamontagne/sensu-chef,sensu/sensu-chef,cwjohnston/sensu-chef,klamontagne/sensu-chef