Set up some tests with `ktest`

[ayberkt]

At this point we can start testing our K operational semantics by adding some hand-written GHC Core programs.

To use ktest for testing, we should specify the designated output in the x.out file in test/pkore-samples for the following hand-written GHC Core programs.

• [ ] Case-2.pkore
• [ ] Case.pkore
• [x] Identity.pkore
• [x] Lambda.pkore
• [ ] Let-1.pkore
• [x] Let-2.pkore

[ayberkt]

@bmmoore can you verify some time that the output files Identity.pkore.out and Lambda.pkore.out are indeed what should be expected? We looked at them with @lucaspena yesterday and decided that they look fine, but it would be nice if you take a look as well.