message: added node v6 details to readme
  Reviewers: benchan
  Subscribers: ben
diff: @@ -14,6 +14,9 @@ Please join us on our [Slack channel](https://slack.bitgo.com) if you have quest
  # Installation
  +Please make sure you are running at least Node version 6 (`6.9.5` recommended) and NPM version 3 (`3.10.10` recommended).
  +We recommend using `nvm`, the [Node Version Manager](https://github.com/creationix/nvm/blob/master/README.markdown#installation), for setting your Node version.
  +
  `git clone https://github.com/BitGo/BitGoJS`
  `cd BitGoJS`
  