Points to improve your code.

[MT-276]

1. Add comments to your code. It is kinda unreadable for a non-programmer.
2. Why do you have a separate file for MP4-MP3 conversion function ? Just merge it into the functions file.
3. If your code is open source then what is the point of your copyright ? Remove your copyright and add a "Free use" licence
4. Add a GUI. Use tkinter. Should be pretty straight forward and easy to just add a simple UI for the options and the quality.
5. Add a requirements.txt or mention the third-party libraries needed to be installed for this program to work.
6. And finally listen to the pull requests. Some them are really good and can improve the overall experience of your project.

MT-276