fix for command line encoding parameters being ignored

Previously both source and target encodings were necessary for using the
correct BabylonBglParser constructor. This fix makes them optional and
will use the detected encoding if not provided. This fix also enforces
the BabylonBglParser object to use the command line provided encodings.
Merge pull request #2 from selfsimilar/master

Possible fix for command line options - please test.