Implement initial processors

Right now, this is just some very simple processors for tags and extra info. Extra doesn't recurse unfortunately, because I'm most likely going to need to use the `reflect` package and I didn't want to go there.

Specifically, given a `map[string]string`, I cannot type assert to `map[string]interface{}`, so I can't just make a general recursive map scrubber. :confused:

I didn't do anything for the User or HTTP interfaces, but I will when I get some bandwidth.

Let me know what you think @titanous!