message: Add Yarn instructions
diff: @@ -52,6 +52,10 @@ Meanwhile, the package can be installed from Github:
  `npm install --save XeroAPI/xero-node`
  +While this codebase is under development, we recommend using Yarn to ensure your builds are repeatable:
  +
  +`yarn add https://github.com/XeroAPI/xero-node`
  +
  ### Config Parameters
  | Parameter | Description | Mandatory |
  