added failing test case

minimized an error in my project to this example. something doesn't seem right as it fails silently and doesn't generate any ./out directory at all. i feel like i'm missing something as wtf.

```
npm test

> docpad-plugin-marked@2.2.0 test /home/michael/repos/docpad/docpad-plugin-marked
> node ./out/marked.test.js

marked
marked ➞  create
marked ➞  create ✔   
marked ➞  load plugin marked
marked ➞  load plugin marked ✔   
marked ➞  generate
marked ➞  generate ➞  action
marked ➞  generate ➞  action ✔   
marked ➞  generate ➞  results
marked ➞  generate ➞  results ✘  
marked ➞  generate ✘  
marked ✘  

FAILURE: 3/3 tests ran successfully; 0 failed, 0 incomplete, 1 errors

Error #1:
marked ➞  generate ➞  results
Error: ENOENT, readdir '/home/michael/repos/docpad/docpad-plugin-marked/test/out'

npm ERR! Test failed.  See above for more details.
npm ERR! not ok code 0
```