Host the release binaries in the project itself

GitHub lets you attach binaries to releases these days, so host them right here instead of on bitbucket + in another repository.

Two notes:
 * The exporter's filename is unversioned while the runtime's is since it came from a maven repo. I could argue either way being more appropriate here, but took the path of least resistance and left things as they were for the moment
 * It's really unfortunate that it looks like they don't provide a redirect so you can ask for the latest release's version of some file name. It makes sense, but also means you link to a specific version from something like this readme when you really want whatever's latest. Again, path of least resistance and ignoring it for now.