Drop Xcode 5.1 and Xcode 6.0 rspec tests

The rspec tests are taking a long time which is slowing down development.

I decided to drop Xcode 5.1 and Xcode 6.0 regression tests.

* Xcode 5.1 - No one should be using this and we should not support it.
* Xcode 6.0 - We support this, but users should be moving to Xcode 6.0.1 or Xcode 6.1