Divide rspec tests into fast unit-style tests and slow integration-style tests that launch the simulator

When developing, we want to use Guard to automatically run the rspec tests.  At the moment, this is impossible because many rspec tests open/close the simulator and launch applications on the simulator and connected devices.  When the simulator launches, it becomes the active application so running the tests means the end of productivity.

Following the example from @michaelkirk in calabash/calabash-ios.