RSpec 3

Last week, I was the first one to stick RSpec to 2.99. Now, Ive used the [transpec tool](https://github.com/yujinakayama/transpec) (really because I wanted to find out how well exactly it would work on alchemy) to transition the test suite. It worked really well, I think. 

So there's two commits that contain exclusively generated code, and a couple of others where I manually removed deprecation warnings.

I added the gem 'rspec-activemodel-mocks' since apparently that functionality is factored out in RSpec 3. 

I didn't yet upgrade to RSpec 3.