Added additional gun types and stat fields.

[enragedginger]

Hi, thanks for putting this repository together. I was toying around with building my own replay parser in Clojure and parts of your library were helpful to have as a reference. I found a few more gun type values and post-game stat values in the replay file and decided to contribute those back to your project. I don't have C# installed, so I haven't compiled and tested this exact implementation, but it should give you a good starting point if you pick this project up again. I'd love to see what you come up with for doing parsing of the checkpoint and replay-data chunk types.