Simplify target

[franciscogouveia]

Taken from franciscogouveia/hapi-rbac#17

Instead of

target: ['all-of',
  {
    type: 'credentials:username',
    value: 'fgouveia'
  },
  {
    type: 'credentials:group',
    value: 'writer'
  }
]

Do something like this for an AND condition

target: {
  'credentials:username': 'fgouveia',
  'credentials:group': 'writer'
}

Use an array for a combination of AND and OR condition

target: [
  {
    'credentials:username': 'fgouveia',
    'credentials:group': 'writer'
  },
  {
    'credentials:username': 'anonymous',
    'credentials:group': 'reader'
  }
]