Making Tutorial notebook easier to run on colab directly

[jalammar]

To make the Tutorial run on Google Colab, I had to add the two commands to install dependencies:

!sudo apt-get install fluidsynth
!pip install pretty_midi mir_eval pyfluidsynth

In case it could make it easier for folks to run the Tutorial notebook, I've added them to the top (commented), and linked to the colab in the README. PR just in case it can make it easier for new users to quickly run for the first time.

[Images in the diff should be unchanged, not sure why/how the editor changed them]

[craffel]

Thanks Jay! Some small changes requested.

[craffel]

Thanks Jay!

[jalammar]

Thank you! I was delighted to find the package and how easy it looks. I had always wanted some programmatic way to experiment with sounding out chords and chord progressions, and some freedom of moving MIDI around. Appreciate the effort you and all the contributors put into this!