Schema conversion

This contains a script for combining `metadata.json`, `details.json` and `links.json` schemas into a single overall schema.

https://trello.com/c/QdWO5hjC/82-automate-schema-verification
Could this be simplified to this?

```ruby
  def combine_definitions
    [metadata_schema, details_schema, links_schema].compact.inject({}) do |memo, embedded_schema|
      memo.merge(embedded_schema.schema.fetch('definitions', {}))
    end
  end
```