[TASK] Finalization
 - fixed bug with reading and writing to WAV files with more than one
   channel
 - fixed bug with reading non-valid data from WAV file
 - added new knob-handling option - range of options is now supported
 - added testing data - tester.sh - performs few execution of the main
   program with sound files from new tests/ directory
 - deleted unnecessary files
 - added more comments