fixes file path issue for windows in setFirmwareNameAndVersion

This is a fix for [issue #4](https://github.com/firmata/arduino/issues/4). It's sorta hacky but it's the best I could come up with. There was also a request (and proposal) to add a new method to manually set the firmware name. That could be added as well via a separate request if people think that functionality is important.

UPDATE: 8/4/13
Updated per recommendation from @kisoft in comment for [issue #4]. Tested on OS X and Windows 7. Should be good to go.