added support for all webhooks in 2013-08-13 and deep merging

I needed support for the webhooks offered in 2013-08-13, so I added them in here.  All supported webhooks are here, not just a subset.

I also needed a way to explicitly set specific attributes, not just globally replace all keys with a new value.  Specifically, I needed to replace some ids deeply nested into the hash, and I couldn't use your method of key replacement.  So I added a deep merge option as well.  It's documented in the README.