Demo: HP4 running test_hub; two tests:
- h1 ping h2 (expected: success)
- h1 ping h3 (expected: fail)
Both tests return the expected results.

To run: sudo ./test.py.

Additional tests may be added with 1-3 files per need:
- <proj>.p4
- [<proj>.commands] -- bmv2 runtime table management commands
- [<proj>.py] -- test cases + mininet script

If the <proj>.py file is not present, the framework uses
test_mininet.py with the two tests described above (h1 ping h2,
h1 ping h3).