Fix dependencies for plain Go example.

The Go example's dependencies were broken. I'm guessing someone set them up using submodules and then someone else broke those.

Right now the Go example only uses a single external dependency (``github.com/go-sql-driver/mysql``), which I've locked into the most current version using git submodules. I've also cleaned up the old, unused dependencies, including some compiled code someone had accidentally checked into the repo.

I don't have the time/machines to run the benchmarks myself, but I'm pretty sure this will fix the issue.

It would be *really nice* in the future if benchmarks which didn't execute cleanly were listed as such instead of dropping off of the list. It was easy to imagine that you'd come up with reasons to not test plain Go, but it turns out someone had accidentally broken the build system and no one got around to fixing it.