Fix for #70 breaks creates duplicate references

[whitlockjc]

When we resolve references recursively, we only want to do this for references that point outside of where we would already be resolving references. What is happening now is that extra references are being recorded in the metadata, which impacts resolution, because we are walking references already intended on being walked. Here is an example:

{
  definitions: {
    A: {
      allOf: [
        {
          $ref: '#/definitions/B'
        }
      ]
    },
    B: {
      allOf: [
        {
          $ref: '#/definitions/C'
        }
      ]
    },
    C: {}
  }
}

reports 3 references instead of two:

#/definitions/A/allOf/0
#/definitions/B/allOf/0
#/definitions/A/allOf/0/allOf/0

The reason for this is we are recursively processing the reference at #/definitions/A/allOf/0 twice, once normally and once as a result of trying to make sure we resolve references outside of where a remote reference might point.