MergeAllOf takes items into account

[jderusse]

This PR allows

      allOf:
        - type: array
          items:
            type: object
            properties:
              id:
                type: string
        - type: array
          items:
            type: object
            properties:
              name:
                type: string

And render it as

      type: array
      items:
        type: object
        properties:
          id:
            type: string
          name:
            type: string

[coveralls]

Coverage decreased (-0.05%) to 81.601% when pulling 7a64873 on jderusse:fix-all-of-array into 6b1e8e7 on Rebilly:master.

[RomanHotsiy]

LGTM! Nice job 👍
Thanks @jderusse