Validator is not checking is "items" key is present for "array" data types

[AlstonLin]

For example this will pass the validator

...
foo:
    type: array
...

However, this should fail according to the swagger specification as items is a required key for any array types

[bplotnick]

@macisamuele I think this was duped by #94 and fixed in #95, right?

[macisamuele]

@bplotnick you are correct. Closing this as duplicate of #94