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'm starting to think we should drop `its`, I want to stay consistent with the `it` blocks. I really did like the way `its` formatted the test output, but we can easily tailor the descriptions to output similar, comprehensive documentation (plus one less gem's lifeline to worry about). What do you think?