Add a tutorial on Game of Life activity

[llaske]

Add a tutorial to the Game of Life, is specifically important to give rules of the game as specified in Wikipedia:
Every cell interacts with its eight neighbours, which are the cells that are horizontally, vertically, or diagonally adjacent. At each step in time, the following transitions occur:

• Any live cell with fewer than two live neighbours dies, as if by underpopulation.
• Any live cell with two or three live neighbours lives on to the next generation.
• Any live cell with more than three live neighbours dies, as if by overpopulation.
• Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.

[llaske]

A full tutorial to integrate a tutorial into an activity is now here https://github.com/llaske/sugarizer/blob/dev/docs/tutorial_step9.md

[llaske]

Fixed in #527