message: update readme to reflect node 8
diff: @@ -63,7 +63,7 @@ While third-party Cardstack plugins are heartily encouraged, the plugins in this
  In development, we use `lerna` to manage the inter-dependencies of all the packages. To get started:
  - 1. Install node >= 7.
  + 1. Install node >= 8.
  2. Install yarn >= 0.28 (earlier versions work but will not benefit from [Workspaces](https://yarnpkg.com/blog/2017/08/02/introducing-workspaces/).
  3. `yarn global add lerna` (use >= 2.0.0 for yarn workspaces integration)
  4. `lerna bootstrap`
  