Comments and suggested changes 

Nice work on this. You were very close to having everything working; just a few small changes here and there were needing to get adding and updating of produce items working. The changes I've suggested here address the adding and updating problems for the produce only; I haven't made the analogous changes for farmers and events.

I recommend looking at each of the commits below individually, the important ones are listed below

Microdata fixes:
* [Fix the relationship between the list of produce items each individual produce item](99caab5)
* [Do not include property labels inside property values](da2e0e2)

API fixes:
* [Search over the names of produce items, not their release dates](a61f1b3)
* [HTML forms can send POST requests without the help of JavaScript](7716cb6)
* [Use POST, not PUT, to add items to the produce list](9c35e56)
* [Not every property of new produce item needs to be required](2f18ea4)
* [Fix updating of produce](af4a076)