Add link resource
Add unit test for link resource
Add integration test for link resource
Update dependency on serverspec and specinfra
Extract run_command and run_specinfra to Backend class.
Backend#run_command accepts Array as an arg.
Refactor Runner class.
Refactoring.
Merge pull request #18 from mizzy/link-resource

Add link resource
Fix a bug.
Bump up version.
Improve showing difference of directory resource.
Show file diff.
Bump up version.