Issue 73: ensure responses is populated with an object

[todanator]

#73

This issue accounts for instances where there are extensions in the responses object and those extensions can be null.

[JamesMessinger]

Good catch! Thanks for the PR!

[wickedest]

@BigstickCarpet , any chance of cutting a release?

[alasdairhurst]

@todanator @BigstickCarpet Problem with the solution is that any keys inside the responses object will still be parsed/validated as responses if they are not null/undefined.
Extensions such as "x-foo" won't be ignored.

responses: {
   "x-foo": {
    "notaresponse": true
  },
  "200": {
  }
}

The same problem may also be seen in paths and parameters.

[JamesMessinger]

Good point, @alasdairhurst . That's a separate issue though, since it applies to the all of the validation logic, not just the response validation. The validator should ignore x- properties everywhere.

[JamesMessinger]

@wickedest - I just released v4.0.0, which includes this PR. Thanks again for the help!