Change the accounts API to represent SF Fire's structure

[trabianmatt]

SF Fire doesn't use subaccounts, so we'll move towards that structure for the initial implementation.

Example implementation:

GET /members/[member_id]/accounts.json

Returns a list of accounts for the member specified by member_id.

Example response with subaccounts

[
  {
    "id": "123456-S01",
    "name": "Savings",
    "balance": "12,345.32",
    "available_balance": "12,243.45"
  },
  {
    "id": "123456-S10",
    "name": "Checking",
    "nickname": "Primary Checking",
    "balance": "3,987.32",
    "available_balance": "3,801.45"
  }
]

[trabianmatt]

This has been updated in the wiki:

https://github.com/trabian/hyperlocal-api/wiki/ApiAccount