Correct some docstrings
Avoid “dead-end” chains with markov_forward
e.g., saying “what do you think of sleep” should not return
a reply consisting of just “sleep” because a terminator
chain happened to be chosen to follow the output word “sleep”
Pattern: “Today's rules”: Reduce chances of failed generation

Try a different seed phrase each attempt instead of sticking
with the same one (which is more likely to come up with all
already-used sentences which will be rejected)