- Unbreak the three broken tutorials (fixes#848)
- This involved a rewrite of PPP-01-10 because I already had my own
solution to that one and I couldn't easily tell what was going
wrong with the previous solution.
- Add assertions to all the tutorials so that non-raising means success
- Add the TTT examples to `test_examples.py` added recently for #909
- Also added sympy to development dependencies since one of the TTT
examples uses it.