Get a list of all Sub Accounts.

{
  "statusCode": 200,
  "subAccounts": [
    {
      "accountNumber": 58324,
      "creditBalance": 201.4,
      "firstName": "Jon",
      "loginName": "jon@castleblack.com",
      "surname": "Snow"
    },
    {
      "accountNumber": 98676,
      "creditBalance": 1936,
      "firstName": "Daenerys",
      "loginName": "khaleesi",
      "surname": "Targaryen"
    }
  ],
  "timeStamp": "20170117054658978",
  "version": "1.0"
}