Fixed error with rmtree

When temp dir contains files with non-ascii characters in the filename, download fails because `rmtree` would raise an exception

    13:48:41 T:2664576064   ERROR: EXCEPTION Thrown (PythonToCppException) : -->Python callback/script returned the following error<--
        - NOTE: IGNORING THIS CAN LEAD TO MEMORY LEAKS!
        Error Type: <type 'exceptions.UnicodeDecodeError'>
        Error Contents: 'ascii' codec can't decode byte 0xe2 in position 33: ordinal not in range(128)
        Traceback (most recent call last):
          File "/home/xbian/.xbmc/addons/service.subtitles.argenteam/service.py", line 321, in <module>
            subs = download(params["id"],params["link"], params["filename"])
          File "/home/xbian/.xbmc/addons/service.subtitles.argenteam/service.py", line 225, in download
            shutil.rmtree(__temp__)
          File "/usr/lib/python2.7/shutil.py", line 241, in rmtree
            fullname = os.path.join(path, name)
          File "/usr/lib/python2.7/posixpath.py", line 80, in join
            path += '/' + b
        UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 33: ordinal not in range(128)
        -->End of Python script error report <--

If we encode `__temp__` before calling `rmtre` the error is fixed.