<div class="container">
  <%= erb :"exercises/_navigation", locals: {exercise: exercise, active: 'readme' } %>
  <%= md(exercise.readme) %>
</div>

<div class="container">
  <%= erb :"exercises/_navigation", locals: {exercise: exercise, active: 'readme' } %>
  <%= md(exercise.files["README.md"]) %>
</div>

Normalize usage of README api endpoint
Normalize usage of README api endpoint

The x-api returns a files array for both the readme and the test suite. Use
the README from there.
