agent2 docs for exception handling

[William la Forge]

https://github.com/laforge49/agent2

I've got exception handling working. In fact, everything in the API is now working--all 5 functions! :D

Still there are things to add, of course, for improved robustness. I can think of just too many ways I can break this code. But at the moment I am thinking that I should add some examples to the API.