Bug/schema and types

Hi Alec,

There is a problem if schema is defined in types or traits. I figure out in my last pull request ( #36 ).
Example:

```yaml
resourceTypes:
 - collection:
    post:
      description: Create a new <<resourcePathName | !singularize>>
      body:
        application/json:
          schema: <<resourcePathName | !singularize>>
```
This will throw a JSON exception.
I fix this by parsing schema only in resources instead of all definition. But maybe i'm wrong.