Modification for #695

[ILer32]

Problem:

• The summary messages are incorrect (assertions, passed, fails, and n_tests are wrong for some sample codes)
• "expect(fatal(false));" counts fails for 2 times
• README.md could be updated

Solution:

• Correct the calculation process for different results (assertions, passed, fails, and n_tests)
• Introduce test_result.fail_tests to count the failed n_tests
• Update README.md

Issue: #695

Reviewers:
@kris-jusiak

[kris-jusiak]

thank you @ILer32

[ILer32]

@kris-jusiak, thank you for your timely review and merge. I enjoyed the process and studied the program during coding.
I may post issues and Pull Requests in the future.
Feel free to mention me and edit my Pull Requests as needed.