Minor "quality of life" improvements

[Gnu-Bricoleur]

I really like your repository and it's a great starting point to generate music with a neural network however, i found that there were few things unclear to me when i first tried to run it, hopefully, this makes things a little bit clearer. Mainly, this pull request allows to select which weight file to run when starting the predict.py script I also edited the Readme file to explain this and prevent users to repeatedly run the predict.py script with the default weight file