Switching to RSpec for testing

This is the first installment of the potential switch, it illustrates the format of model testing. If anyone has any input on how I can make these tests even better, while maintaining readability, I would really appreciate the help. I purposely only tested one method so that we can focus more on the style versus what is actually being tested. I'm hoping to decide on a style before this PR is merged.  @ferrous26 @zhangsu
I was trying to do that earlier. I ran transpec to convert, and it said everything was fine but all my tests failed when I switched to 3.0.0. It didn't recognize stub_model. I put that on hold to look at something else for the moment. I am definitely for the straight switch to RSpec 3.
We don't need its, I replaced it with expect. Unless you feel strongly about it.