Fixed ActiveSupport::Notifications subscr in Log

ActiveSupport::Notifications subscription should be properly
namespaced to avoid conflicts
Naive specs to cover core modules
Merge pull request #53 from arax/log_fix

Fixed ActiveSupport::Notifications subscr in Log
Avoid assigning model if it does not exist
Links specs
Testing convert() method indirectly
Merge pull request #54 from sustr4/specupdate

Specs and small fixes