Example doesn't seem to work on macOs.

Hi,

I didn't manage to get the example to work on macOs:

![image](https://cloud.githubusercontent.com/assets/99779/23114511/50aadd7a-f7a4-11e6-8c65-759c2a3151a6.png)

The Python end seems to be fine though:

```bash
(python-2.7) Kali:electron-python-example kelsolaar$ python pycalc/api.py
start running on tcp://127.0.0.1:4242
```
