Improve compression

[alexose]

(Sorry to open up all these issues! I promise to also file PRs for them)

Due to overhead, using zlib to compress short strings usually results in an overall longer message.

I've done a bit of research into this, and I think the best solution is the UniShox2 library. I implemented this in my better-compression branch and have had solid results.

Here's a browser-based demo I put together if you want to see it in action.

[brendon-stephens]

This is great, thanks for sharing.