add piazza simple fixtures

[jsshafer]

No description provided.

[jsshafer]

add simple fixtures from piazza posts.

[baileyparker]

Hey Justin! Thanks! These look good! If you check the TravisCI details, it'll give you some pointers about how you can clean up the tests:

• It seems that two sim files binary2.sim and modErr.sim are missing *.ast files. It looks like you wanted these to error. In that case, you should create a binary2.ast and modErr.ast with a single line beginning with error: (you can add a helpful human readable description to explain to someone who fails your test why it should have errored, the harness won't check that the error text matches)
• It seems like you have included a duplicate random.sim. It's already covered in: https://github.com/baileyparker/phf-compilers-tests/blob/d58fd96000027413be3fab4f43cb55588f074d13/simple_test/fixtures/random.sim so it should be safe to remove your duplicate

If you can push commits fixing these two things then this is ready to merge.

Thanks so much! 😃