Added HTML canvas and functions to initilize a rectangle which will be the game board
Created constructors for tile and snakehead objects and added functions for creating the first snake head and update the game board array

The first snake head is put in the snake array and then the separate function for updating the game board array resets all current snake-flags
and loops through the snake array and adds snake-flags for the new snake items.
Updated drawGUI (prev. drawGameBoard) with code to loop through the game board array and draw tiles accordingly to the flags
Removed comments
Centered the game board horizontally and added top margin
Floored the coordinates of the first snakehead so that it doesn't has decimals
Fixed offset bug where the snake is drawn below the gameboard

Placing a snake body item in y-coordinate 0 would draw the snake one game pixel below the board instead of on the first row. This was due
to rectangles in canvas being drawn downwards, while I have chosen to use a traditional y/x-axis grid which goes up and to the right
(instead of down and to the right). Seems more logical this way. Fixed it by setting the y-offset to minus one game pixel when drawing the snake.