publish go-livepeer to Homebrew

Now that we're releasing new semver-tagged releases regularly, it would be great if we could get the latest version of Livepeer with brew install livepeer.

Three ways to accomplish this, as far as I know:

• Submit a pull request to homebrew/core with a script capable of downloading and installing go-livepeer (Docs). This would work fine but I think will require us to build successfully with Brew-provided gnutls and ffmpeg, as I'm not sure that the stuff we do in ./install_ffmpeg.sh is kosher in this context.
• Add a Homebrew cask, such that users could do brew cask add livepeer or some such.
• Create and maintain our own Brew tap, which just downloads the binaries from GitHub. This allows for full customization but it means it's up to us to provide the infrastructure and everything.

Getting into homebrew/core is ideal as it will cause us to show up when folks do e.g. brew search livepeer but we can go with one of the other methods if it's troublesome. My only opinion: let's publish as livepeer rather than go-livepeer, just like the binary already is.