Instructions
type "make assign3" to compile
type "make run" to run
type "make all" to compile and run

Enhancements:

- support save and load of the entire animation: clicking "save" button to save model in "sketch.sav", you can close the program and load from previous save.

- support 4 different colours as well as 6 stroke sizes

- added a eraser circle in erasing mode

- dyed selected shapes green

- slider will double when time exceeds its maximum value