ResourceTypeSchema fails when loading resource definitions using 'oneOf', 'if' keywords

[vladtsir]

Error:

java.lang.ClassCastException: org.everit.json.schema.CombinedSchema$Builder cannot be cast to org.everit.json.schema.ObjectSchema$Builder
	at software.amazon.cloudformation.resource.ResourceTypeSchema.load(ResourceTypeSchema.java:110)

To reproduce create a schema file as follows:

valid-with-oneof.json:

{
  "typeName": "AWS::Test::TestModel",
  "description": "A test schema for unit tests.",
  "sourceUrl": "https://mycorp.com/my-repo.git",
  "properties": {
    "propertyA": {
      "type": "string"
    },
    "propertyB": {
      "type": "string"
    }
  },
  "oneOf": [
    { "required":  ["propertyA"]},
    { "required" : ["propertyB"]}
  ],
  "primaryIdentifier": [
    "/properties/propertyA"
  ],
  "additionalProperties": false
}

public void validSchema_withOneOf_shouldSucceed() {
        JSONObject resource = loadJSON("/valid-with-oneof.json");
        final ResourceTypeSchema schema = ResourceTypeSchema.load(resource);
}

[PatMyron]

@vladtsir does #81 fix this?