removed duplicate instruments Closes freakimkaefig/Music-XML-Analyzer#48
removed duplicate instruments Closes freakimkaefig/Music-XML-Analyzer#48

freakimkaefig/Music-XML-Analyzer,freakimkaefig/Music-XML-Analyzer,freakimkaefig/Music-XML-Analyzer,freakimkaefig/Music-XML-Analyzer,freakimkaefig/Music-XML-Analyzer,freakimkaefig/Music-XML-Analyzer