Incomplete type definition for array/Collection properties

NOTE: cleaved off of #34

---

This bug seems not to be completely fixed. It doesn't throw a NPE anymore, but it doesn't generate the schema correctly either. It just generates:

``` json
{
"type":"array"
}
```

I extended the test to use a collection of nested beans, and expected to see the schema of the nested items, e.g.:

``` json
{
"type" : "array",
"items" : {
"type" : "object",
"properties" : {
"property1" : {
"type" : "integer"
},
"property2" : {
"type" : "string"
}
}
}
}
```

See updated test: https://github.com/greyfairer/jackson-module-jsonSchema/commit/2a9b859fac14a412de68917655c9cf928d31d651