WIP: Make HAL formatter strict.

#186 

Just playing around with some code...
no just check that the variable is set. 

$curies_name = variable_get('restful_hal_curies_name', 'hal');
$resource_name = ($curies_name) ? $curies_name . ':' . $resource_name : $resource_name; 

do the same check for the curies link. . .