MetricResult using ActiveRecord.

signed-off-by: Alessandro Palmeira <alessandro.palmeira@gmail.com>
signed-off-by: Rafael Manzo <rr.manzo@gmail.com>
signed-off-by: Renan Fichberg <rfichberg@gmail.com>
MetricResult associated with ModuleResult.
Fixed ModuleResult specs after rebase
ModuleResult refactored to use ActiveRecord association for MetricResult retrieval
Removed unecessary test introduced by 717ab03fc5aee849e3dcf13a706e3da8bf4b26b2