Fix array items are not validated against additionalItems when items is an array

[bugventure]

Given the following conditions for an array schema:

1. items is an array of item schemas (for positional child item validation);
2. additionalItems is a non-empty object defining a schema;
3. The validated array has more items than specified by the items array in the schema;

In this scenario, validation does not take into account additionalItems when validating additional array items.

JSON Schema reference: http://json-schema.org/latest/json-schema-validation.html#anchor131