WINDOWS: PRE REQ
MAC: PRE REQ
- make sure xcode is up to date. http://stackoverflow.com/questions/15417619/how-do-you-update-xcode-on-osx-to-the-latest-version
- make sure you have brew https://brew.sh/
- make sure you have node installed http://stackoverflow.com/questions/28017374/what-is-the-suggested-way-to-install-brew-node-js-io-js-nvm-npm-on-os-x
- brew install yarn