Removed special bytes conversion for Python 3

With the current Python (3.3.0), this conversion to bytes in the run method before sending data to the subprocess module resulted in

AttributeError: 'bytes' object has no attribute 'encode'

in subprocess. Without the extra conversion, the run method performs smoothly in Python 3.3.0. The change should not effect Python 2 behavior, as the conversion was only triggered for Python 3 in the first place.