bumped .buildpacks to give ddollar/heroku-buildpack-multi a whirl
last releaase didn't build mdbtools. trying to ommit ruby this time to test forcing the issue
fixed BUILDPACK_URL in heroku config to point to https://github.com/ddollar/heroku-buildpack-multi.git (it was incorrectly set to https://github.com/heroku/heroku-buildpack-ruby)
added missing unicorn gem referenced in Procfile
removed unicorn altogether
updated readme