Why is phoenix_ecto failing to compile on the :model in the changeset?
<p>When I try to run <code>mix deps.get</code> or <code>mix deps.compile</code> I get this error:</p>

<pre><code>== Compilation error on file lib/phoenix_ecto/html.ex ==
** (CompileError) lib/phoenix_ecto/html.ex:3: unknown key :model for struct Ecto.Changeset
    (stdlib) lists.erl:1354: :lists.mapfoldl/3
</code></pre>

<p>Why is this happening and how can I fix it? </p>