Fix "Download as resume.json" for Firefox users

Hi there,

In Firefox, clicking the Download button triggers a ReferenceError:

~~~
ReferenceError: event is not defined file.js:29
~~~

Indeed there is no `event` variable here. I modified the mouse event initialization to use dummy values (`0` and `false`), and it now works as intended.

- Before: on OSX 10.9, Chrome 39 (OK), Safari 7 (OK), Firefox 34 (KO)
- After : on OSX 10.9, Chrome 39 (OK), Safari 7 (OK), Firefox 34 (__OK__)

Thanks for this tool by the way!