Prototype implementation of #104
Fix for backward compatibility
Support fluent interface with chain for type explicit subject
Add specs for service type subject

Also fixed how to include modules and how to run specs.

The syntax ``:os => :xxx`` doesn't work with eplicit typed subjects.

So I separete specs into per OS and include OS helpers explicitly
Add to_s for readability of results of specs
Merge pull request #105 from mizzy/explicit-subject-type

Specify subject type explicitly