make a transport module and use freedom message passing to drive the app

This re-packages the throwaway code I was using to send UDP datagrams as a Freedom module. This isn't really the part I want to focus on right now -- so the module is still just throwaway code -- but I found it useful to get things a little closer to how they will eventually work, which will be based on Freedom message passing (and this may become a transport provider, and this is probably the part that should expose the obfuscation and deobfuscation API.......for sure, this should be in a separate module from the TURN relay).

Also, use the arraybuffer utilities from:
https://github.com/uProxy/build-tools/pull/1