Unable to reference in array items in parameters

Hi,

first I want to say: thank you - for your open source work.
Second: I must blame myself as completely new to this whole flask, rest, swagger thing,
so maybe it is just my fault, but after trying several days all possible variations I'm very lost now.
So third - "the" problem:

when I expand your `examples/test_validation.yml` with
```
diff --git a/examples/test_validation.yml b/examples/test_validation.yml
index 66b3508..3094847 100644
--- a/examples/test_validation.yml
+++ b/examples/test_validation.yml
@@ -27,6 +27,18 @@ parameters:
default: ["wizard", "hogwarts", "dead"]
items:
type: string
+ myobjects:
+ type: array
+ items:
+ $ref: '#/definitions/MyDefinedObject'
+
+definitions:
+
+ MyDefinedObject:
+ type: object
+ properties:
+ myProperty:
+ type: string

responses:
200:
```
[test_validation_working_docs.txt](https://github.com/rochacbruno/flasgger/files/963789/test_validation_working_docs.txt)

than the documentation looks perfect and matches the specification.
But unfortunately when I try with:
```
curl -X POST -H "Content-Type: application/json" -d '{
"age": 180,
"tags": [
"wizard",
"hogwarts",
"dead"
],
"username": "Sirius Black",
"myobjects": [
{"myProperty": "somevalue"}
]
}' http://127.0.0.1:5000/autovalidation
```
the response is: `RefResolutionError: Unresolvable JSON pointer: u'definitions/MyDefinedObject'`.

I can get it to work without the array definition around my custom type, but I really need an array here.

Any kind of comment, suggestion, help or at least some pointers into a direction would be very welcomed !