adding info to the readme (requirements and installation)
adding info to the readme (requirements and installation)

Leimi/drawingboard.js,Leimi/drawingboard.js,zartata/drawingboard.js,zartata/drawingboard.js,Leimi/drawingboard.js,zartata/drawingboard.js,mattjmattj/drawingboard.js,mattjmattj/drawingboard.js