Update README.md

[DaveGUI]

Added to the README/documentation on how to use Flask-Compress with caching using an example. I couldn't find any examples online(including no unit tests covering it) so I had to dig into the flask-compress code to figure out how to use them together. Therefore wanted to document it so others can choose to use it (or not). On my server using caching gave me another 10-20% performance improvement above the improvement given by Flask-Compress when serving both static files and dynamic large data(json).

[alexprengere]

Thanks! I just had to fix some markdown formatting in a subsequent commit (code blocks use backticks, not quotes).