mustache command works with pure json files

Running with testing files [1] produces the expected output:

```shell
  + ./mustache demoyaml.yml demo.html.mustache
  <h1>Colors</h1>

      <li><strong>red</strong></li>
      <li><a href="#Green">green</a></li>
      <li><a href="#Blue">blue</a></li>

  + ./mustache demo_json_object.yml demo.html.mustache
  <h1>Colors</h1>

      <li><strong>red</strong></li>
      <li><a href="#Green">green</a></li>
      <li><a href="#Blue">blue</a></li>

  + ./mustache demo_json_array.yml demo.html.mustache
  <h1>Colors</h1>

      <li><strong>red</strong></li>
      <li><a href="#Green">green</a></li>
      <li><a href="#Blue">blue</a></li>
```

[1]: https://gist.github.com/cheecheeo/10440392