malformed or unreadable swagger supplied

Okay, that one was a bit tricky. Under your Employer definition you have:

    locations:
        type: "array"
        items:  {
          $ref: "/definitions/Location"
        }

It should actually be (notice the extra #):

    locations:
        type: "array"
        items:  {
          $ref: "#/definitions/Location"
        }

That should solve the issue.

Also, if you want to utilize YAML to the fullest, you can write it all as:

    locations:
        type: array
        items: 
          $ref: "#/definitions/Location"