simple integration test
TODO: allow different language code cells

see http://nbviewer.ipython.org/github/ipython/ipython/blob/1.x/examples/notebooks/Cell%20Magics.ipynb

e.g. the markdown code cell

```bash
find . -name README.md
```

would turn into a code cell with contents

%%bash
find . -name README.md
separate out parser and allow arbitrary regex
allow arbitrary fenced code blocks
allow indented code blocks
command line switch for code block type