Fixed main method to only require two actions: generation of a midi file object and finally a song.
Cleaned up MIDI_File by moving some instance variables to methods.
Finished input stage of composerator. Upload a .mid file (as specified by it's file path) and call the .to_song() function on it and it will return a song object that has 4 chain objects filled with chainable objects that can then be used to create markov chains and eventually the final music.