depends: update the comparison tool to a more recent version

Travis comparison tests sometimes disconnect from bitcoind for some non-obvious
reason. Update them to a more recent version to begin troubleshooting.

As suggested by @TheBlueMatt . Thanks to @mikehearn for the build instructions.

Fetching a pre-built jar from my repo is hardly ideal, but it's no different from what's been done in the past. @mikehearn: Any interest in packaging it alongside bitcoinj releases in the future?