Fressian has absolutely no JavaDoc

[rschmitt]

I'm the author of a library that provides Java bindings for Clojure's data modeling and serialization capabilities. I've been working on adding Fressian support and I've noticed that, other than the StreamingWriter class, the Fressian library is not at all self-documenting. There is some out-of-band documentation on GitHub, but many crucial concepts (e.g. InheritanceLookup) I had to figure out by reading code. It's true that data.fressian is fairly self-documenting, but I'm targeting Java developers who would be coding directly against the Java reference implementation and not the Clojure bindings.