message: Document new tests
diff: Bril: A Compiler Intermediate Representation for Learning
  =========================================================
  -Bril (the Big Red Intermediate Language) is a compiler IR made for teaching a compilers course.
  +Bril (the Big Red Intermediate Language) is a compiler IR made for teaching [CS 6120][cs6120], a grad compilers course.
  It is an extremely simple instruction-based IR that is meant to be extended.
  Its canonical representation is JSON, which makes it easy to build tools from scratch to manipulate it.
  @@ -19,18 +19,13 @@ Tests
  -----
  There are some tests in the `test/` directory.
  -They use [Cram][], which lets us write the expected output for each shell command.
  +They use [Turnt][], which lets us write the expected output for individual commands.
  Install it with [pip][]:
  - $ pip install --user cram
  + $ pip install --user turnt
  -Then run the tests:
  +Then run all the tests by typing `make test`.
  - $ cram test/*.t
  -
  -Or simply:
  -
  - $ make test
  -
  -[cram]: https://bitheap.org/cram/
  [pip]: https://packaging.python.org/tutorials/installing-packages/
  +[cs6120]: https://www.cs.cornell.edu/courses/cs6120/2019fa/
  +[turnt]: https://github.com/cucapra/turnt
  