title: How can I replace the `application:adapter` with a `DS.FixtureAdapter` in my acceptance tests?
body: <p>We're using Ember Data and have a <code>RestAdapter</code>, but we don't want to use this in our tests. 
  How can I replace the <code>application:adapter</code> with a <code>DS.FixtureAdapter</code> in my acceptance tests?</p>