Now that the tests can be run using `cargo test`, update the instructions to reflect this. Signed-off-by: David Brown <david.brown@linaro.org>
Now that we depend on a submodule for mbed TLS code, update the docs to explain how to fetch this. Otherwise, the error is somewhat misleading, just showing a missing sha256.c file. Signed-off-by: David Brown <david.brown@linaro.org>
Describe how to build and run the simulator.