VE-1588: Tests for ve.dm.WikiaTemplateModel

Because we make an API request to get all available parameters for a given template, we need to ensure that we don't add all of the empty parameters in the serialize() and getWikiText() methods. This test tests for this scenario.
Would be good to have more meaningful messages/description - checkout ve.dm.MWTransclusionNode.test.js for inspiration :)