[50588851] cancan's ability definition/usage

Signed-off-by: Henry Chen <hchen@vmware.com>
Merge branch 'master' of https://github.com/vmw-tmpst/heroapp-LetsHire into ability

Signed-off-by: Henry Chen <hchen@vmware.com>

Conflicts:
	app/controllers/users_controller.rb
Merge pull request #203 from Henry-CF/ability

[50588851] cancan's ability definition/usage