Systems mock rev2

This is an updated version of the code on [pull request 15](https://github.com/deltacloud/core/pull/15) - addresses the comments/concerns from [rlandy](https://github.com/deltacloud/core/pull/15#issuecomment-16678629) and [dkoper](https://github.com/deltacloud/core/pull/15#commitcomment-3058431)

thanks, marios