Fixes issue #3, YAML file encoding issue with Ruby >= 1.9.3
Created by: pmorillon
Since Ruby 1.9.3, the default YAML engine is 'Psych' instead of 'Sick'. We can change the engine to Sick, but Sick is not available from Ruby 2.0.0. So, we can use UTF_8 encoding for disk:model and disk:rev attribute to solve the problem.