Fix config var end point generations

Links on resources without properties like "config vars" in the Heroku
platform schema are currently being generated without parameters, even
if they specify that they have parameters in their `href`.

e.g.

``` ruby
  class ConfigVar
    def initialize(client)
      @client = client
    end

    # Get config-vars for app.
    def info()
      @client.config_var.info()
    end

    # Update config-vars for app. You can update existing config-vars by setting them again, and remove by setting it to `NULL`.
    #
    # @param body: the object to pass as the request payload
    def update(body)
      @client.config_var.update(body)
    end
  end
```

This pull removes a check on the `properties` array so that these links
can be properly generated.

``` ruby
  class ConfigVar
    def initialize(client)
      @client = client
    end

    # Get config-vars for app.
    #
    # @param app_id_or_app_name: unique identifier of app or unique name of app
    def info(app_id_or_app_name)
      @client.config_var.info(app_id_or_app_name)
    end

    # Update config-vars for app. You can update existing config-vars by setting them again, and remove by setting it to `NULL`.
    #
    # @param app_id_or_app_name: unique identifier of app or unique name of app
    # @param body: the object to pass as the request payload
    def update(app_id_or_app_name, body)
      @client.config_var.update(app_id_or_app_name, body)
    end
  end
```
Merge pull request #35 from interagent/brandur-fix-config-vars

- Correctly generate code for links with href parameters even when the
  parent resource doesn't have any other properties.