[COOK-4632] - Fix warning message from build-essential

* Renamed the build-essential 'compiletime' attribute to 'compile_time'
* Added more complete unit test coverage of the ruby recipe
[COOK-4632] - Changed node.set to node.default to avoid Chef Server issues
Merge pull request #11 from AMeng/COOK-4632

[COOK-4632] - Fix warning message from build-essential