use svg.py for Piano

https://github.com/orsinium-labs/svg.py

• delete svg pritty print
• border radius
• everything should be customisable - every corner radius, every font-size
• render piano using svg only, without html
• fix ipynb image after page reload, seems to work, see example in Untitled34.ipynb (look inside json to see difference) It kinda depends on size of svg https://www.google.com/search?q=jupyter+resets+svg+after+page+refresh&oq=jupyter+resets+svg+after+pag&aqs=chrome.2.69i57j33i160l3.14160j0j4&client=ms-android-xiaomi&sourceid=chrome-mobile&ie=UTF-8. Trusted is source of issues
• fix text aligh in squares
• fix failing tests with xmlns="http://www.w3.org/2000/svg"/
• add piano cards examples in readme