Make the jardiff.py fully cross-platform

Make the jardiff.py fully cross-platform. Thanks a lot for help me, the script is working on Windows as well as on UNIX platforms :smile:.

I do not know how to program in Python, i'm a .Net guy, some things can get better :smile: in code

In Windows requires Cygwin. After I send another pull request with information about its installation and required package.

Thanks a lot.
This will lead to print a warning such as:
`Warning: Binary file ../XYZ`

Workaround: inside the `javap_public`method:
```
chunk[i] = chunk[i].replace(".class", "")
```